I had a bit of an issue getting things going as I've never played with the fuses before. Maybe this can save someone else some time. If I'm doing something silly here please correct me.

[DISCLAIMER] this worked for me. Use at own risk[DISCLAIMER]

Executed these commands from the subfolder \hardware\tools\avr\bin of my local arduino IDE.
Connected the board ICSP using an USBASP with the latest firmware. Change the "-c usbasp" part if you connect using something else.

Flash bootloader

avrdude -C ../etc/avrdude.conf -c usbasp -B5 -p ATmega328P -U flash:w:..\..\..\arduino\avr\bootloaders\atmega\atmega328_1a.hex

Set fuses

avrdude -C ../etc/avrdude.conf -c usbasp -B5 -p ATmega328P -U lfuse:w:0x62:m -U hfuse:w:0xDE:m -U efuse:w:0x07:m -U lock:w:0x2F:m

I think the B5 was crucial as it slows things down a bit. The bootloader (atmega328_1a.hex) is the one mentioned in the first post. I also added the part in the boards.txt of the arduino IDE.

Now I can connect the board to the FTDI and upload and run sketches without issues.

On to the next step

Just received my boards from DirtyPCB
Enough for 10x3=30 sensors... The boards look nice. I think I can even skip the R&C's if I use the internal VCC measuring method but I'll have to scan the thread for that.

I had a bit of an issue getting things going as I've never played with the fuses before. Maybe this can save someone else some time. If I'm doing something silly here please correct me.

[DISCLAIMER] this worked for me. Use at own risk[DISCLAIMER]

Executed these commands from the subfolder \hardware\tools\avr\bin of my local arduino IDE.
Connected the board ICSP using an USBASP with the latest firmware. Change the "-c usbasp" part if you connect using something else.

Flash bootloader

avrdude -C ../etc/avrdude.conf -c usbasp -B5 -p ATmega328P -U flash:w:..\..\..\arduino\avr\bootloaders\atmega\atmega328_1a.hex

Set fuses

avrdude -C ../etc/avrdude.conf -c usbasp -B5 -p ATmega328P -U lfuse:w:0x62:m -U hfuse:w:0xDE:m -U efuse:w:0x07:m -U lock:w:0x2F:m

I think the B5 was crucial as it slows things down a bit. The bootloader (atmega328_1a.hex) is the one mentioned in the first post. I also added the part in the boards.txt of the arduino IDE.

Now I can connect the board to the FTDI and upload and run sketches without issues.

On to the next step

Just received my boards from DirtyPCB
Enough for 10x3=30 sensors... The boards look nice. I think I can even skip the R&C's if I use the internal VCC measuring method but I'll have to scan the thread for that.

I also ordered the PCBs (at my own risk) and some of "TMK-T20 20mm 17mm"
I'll try to CNC or 3Dprint some endcaps or something.

m26872, I just wanted to say thank you for your work on this project and for sharing it with everybody.
I've just ordered the ATMEGAs to build 5 nodes.
How confident are you about the V1.4 PCB ? If you don't see any issue with them at this point I think I'll take the whopping $14 risk