I'm an experienced embedded developer and I spent weeks tinkering with various things around MySensors. Here are my 2 cents to anybody who wants to start quickly and painlessly.

1. Do not bother with anything but Arduino, nano is especially simple to use due to the built-in USB. I personally prefer pro minis due to the form factor. Do NOT bother with Raspberry Pi, it is too much work to get something done unless you have pre-build images you can just dd on your SD card.
2. Please, if you are starting with Arduino and stuff, USE some shield for your radio module. Order some Nano RF24 shield like this one https://www.amazon.com/Emakefun-Terminal-Expansion-ATMEGA328P-Interface/dp/B07N8PLFVC to avoid self-wiring. nRF24 4x2 header is idiotic and it is easy to make frustrating mistakes, have loose wires, miss a capacitor, have a weak voltage regulator, etc.
3. A serial gateway with a nano on a shield can be put together in 5 minutes. You just stack things up, make sure you CE and CS pins are right and upload a sketch. You are done.
4. nRF24 is a radio on 2.4GHz. Let it sink for a bit. Almost everything wireless (and microwaves) in your house runs on that frequency. Do yourself a favor, run a simple wifi scan on your phone and see which part of the band is messed up and which is available. It is simple to do today with free Android and Apple apps.
5. Watch your signal strength! What do you do when you start dropping packets? Put both modules closer and bump signal UP right? WRONG! That will make it worse and you will go down the spiral trying to figure out why your nRF24 radio is total crap. Closer you get, weaker signal you need. Seriously. If you will be operating the same room, set a signal to LOW. When you will go over one wall, set it to HIGH. I'm using nrf24l01+pa+lna modules (one with antenna) between house and garden, three walls in between, 50 yards, and on LOW I have 100% reliable connection, no dropped packets.

As of now, I'm using these battery-powered stacks (nrf24l01+pa+lna & jModule2 & pro mini 3.3V) around the backyard and I'm happy camper:

@dzjr it depends what do you need it for. This is my 2 cents on 3d printing at the moment.

If you need to print something small with high detail, get an SLA printer like Elegoo Mars. It is cheap, easy to understand and resolution is amazing. Prints out of the box, but it is messy and smelly.

Otherwise:

1. You are a complete noob, you have no clue how that stuff works, you just want to print. Get Prusa and print PLA. Basic printer, not great but reliable and great company support and great community.
2. You are a complete noob on a budget but willing to learn. Get Ender 3 and print PLA. It is basic, cheap, but gets a job done. Community support is great, but expect you will have to tinker with the printer.
3. You are a moderately experienced in tech and you need a workhorse. Get FlashForge Creator Pro or similar and print PLA, PETG or even ABS. Community support is great, that thing is an older design but it just works.
4. You are moderately experienced, with special (tinkering) demands. Here it gets very personal. There is a bunch of RepRap style printers with a moving bed (which I hate). There are some deltas (why??) and there is growing number of CoreXY printers of various sizes (Two Tree, Elf, Tronxy...). I would probably go that route. Stick with PLA and PETG.
5. Geek with time, resources, and curiosity. Build your own CoreXY printer. Voron, Railcore, etc. Print what you want.

I skipped 1) and 2) and went through 3) - 5). I personally own Elegoo, FlashForge CP, Elf, and CoreXY of my own design.

@dzjr To be completely fair, there is one big downside of the FFCP and it is the control board. FFCP is running an 8-bit MightyBoard (MakerBot board) clone which is running Sailfish firmware. That FW is great for what it does on 8-bit UC, but that era is now gone. I still have it, I still use it, but there is and won't be any new development. So sooner or later, you would likely have to replace it with something else.

So, unless you really need to print ABS, ASA, PC, Nylon, or other "hard" stuff, my suggestion is to go with Ender with an open mind (and side budget) that you will do updates. This will get you into the 3d printing quickly and you will learn some valuable lessons without wasting much money. If you find out you like it and you "need some more", I strongly suggest you go for good CoreXY experience.

If you know you need to print for outdoors (ASA) or you will be doing some engineering parts from ABS, PC, or Nylon, forget about Ender and start saving for something better.

@dzjr difference between Ender & FFCP is huge. Let me point out the most important once:

1. Enclosed build volume. You can print ABS, ASA, HIPS, PC, or any other "engineering" materials which shrink a lot and they WILL delaminate if printed on something like Ender.
2. Two extruders mean you can print support structures using soluble filaments. That will give you an advantage in printing complex parts.
3. Z only moves up. Let it sink for a bit. On the Ender, you are moving the entire mass of the print with every Y move. It is a terrible concept and only works for tiny printers.

I understand why people like small RepRap printers (Ender). They are cheap, simple, easy to understand, and easy to fix. But they have serious limits which some people are underplaying. RepRap printers, in general, can never achieve higher print quality than gantry or corexy printers. It is simple physics. Enclosed, they take prohibitive amounts of space compare to their build volume, etc ...

I'm not saying they are bad. Just know your limits. Ender is great if you are on a budget.
Good luck!

Edit: It is also important to mention, that getting "a printer" to where you want it to be, usually costs at least the same amount as the printer itself. So if you buy € 235 printer, expect to spend another ~€ 250 to do upgrades (PEI build surface, better extruder, better hotend, BL-touch, stiffening brackets, ... list never ends). This is not a cheap hobby, really.

@dzjr it depends what do you need it for. This is my 2 cents on 3d printing at the moment.

If you need to print something small with high detail, get an SLA printer like Elegoo Mars. It is cheap, easy to understand and resolution is amazing. Prints out of the box, but it is messy and smelly.

Otherwise:

1. You are a complete noob, you have no clue how that stuff works, you just want to print. Get Prusa and print PLA. Basic printer, not great but reliable and great company support and great community.
2. You are a complete noob on a budget but willing to learn. Get Ender 3 and print PLA. It is basic, cheap, but gets a job done. Community support is great, but expect you will have to tinker with the printer.
3. You are a moderately experienced in tech and you need a workhorse. Get FlashForge Creator Pro or similar and print PLA, PETG or even ABS. Community support is great, that thing is an older design but it just works.
4. You are moderately experienced, with special (tinkering) demands. Here it gets very personal. There is a bunch of RepRap style printers with a moving bed (which I hate). There are some deltas (why??) and there is growing number of CoreXY printers of various sizes (Two Tree, Elf, Tronxy...). I would probably go that route. Stick with PLA and PETG.
5. Geek with time, resources, and curiosity. Build your own CoreXY printer. Voron, Railcore, etc. Print what you want.

I skipped 1) and 2) and went through 3) - 5). I personally own Elegoo, FlashForge CP, Elf, and CoreXY of my own design.

@mhkid here you go: https://www.openhardware.io/view/332/jModule2

I honestly use it for much more than MySensors.
I made myself a little RC transmitter/receiver ecosystem out of the "3.3V Pro Mini + jModule2 + NRF24L01+(PA+LNA)" sandwich.
I have about 4 RC transmitters (mostly made of PS2 analog controller + above) and a bunch of RC receivers (DRV8833 + above) for little boats, cars, robots, or whatnot. If you buy these at bulk, they are under $10 with driver for two motors, you can program them in any way you want and kids can have a lot of fun. And if they break/drown/burn few, I can whip another 5 in a couple of hours.

IMHO 3.3V Pro Mini + jModule2 + NRF24L01+(PA+LNA) + DRV8833 + 2xAA or 1S LiPo battery is very powerful combination, completely customizable, tiny and cheap.
I might make an Instructable for it or something.

I'm an experienced embedded developer and I spent weeks tinkering with various things around MySensors. Here are my 2 cents to anybody who wants to start quickly and painlessly.

1. Do not bother with anything but Arduino, nano is especially simple to use due to the built-in USB. I personally prefer pro minis due to the form factor. Do NOT bother with Raspberry Pi, it is too much work to get something done unless you have pre-build images you can just dd on your SD card.
2. Please, if you are starting with Arduino and stuff, USE some shield for your radio module. Order some Nano RF24 shield like this one https://www.amazon.com/Emakefun-Terminal-Expansion-ATMEGA328P-Interface/dp/B07N8PLFVC to avoid self-wiring. nRF24 4x2 header is idiotic and it is easy to make frustrating mistakes, have loose wires, miss a capacitor, have a weak voltage regulator, etc.
3. A serial gateway with a nano on a shield can be put together in 5 minutes. You just stack things up, make sure you CE and CS pins are right and upload a sketch. You are done.
4. nRF24 is a radio on 2.4GHz. Let it sink for a bit. Almost everything wireless (and microwaves) in your house runs on that frequency. Do yourself a favor, run a simple wifi scan on your phone and see which part of the band is messed up and which is available. It is simple to do today with free Android and Apple apps.
5. Watch your signal strength! What do you do when you start dropping packets? Put both modules closer and bump signal UP right? WRONG! That will make it worse and you will go down the spiral trying to figure out why your nRF24 radio is total crap. Closer you get, weaker signal you need. Seriously. If you will be operating the same room, set a signal to LOW. When you will go over one wall, set it to HIGH. I'm using nrf24l01+pa+lna modules (one with antenna) between house and garden, three walls in between, 50 yards, and on LOW I have 100% reliable connection, no dropped packets.

As of now, I'm using these battery-powered stacks (nrf24l01+pa+lna & jModule2 & pro mini 3.3V) around the backyard and I'm happy camper: