To follow up. It was hardware: broken vcc pin on the dht11 corrupted the whole sensor code badly. Resolder and added wait-code, inverted the on-off 0-vs-1 and I have a good working sensor. The duplicate is also installed and working reliably.
A 6-relay board is also working nicely and Domoticz is great. My old system is nearly replaced and I couldnt be happier.
Respect and thanks all around!
@Yveaux and @boum You two beat me by 2hrs.
@user2684 whose code this is (cudos to him, have used this bit on a number of sensors!) had probably figured that out and I screwed myself when I changed the original analogRead to int.
Now the whole thing works 100%
I've been looking into ESPnow and it looks good to me in many ways. Also the architecture would simplify building sensors.
I'm not a programmer at all, so I have no real idea of the scope of coding & testing this request would require. Or if the protocol could be suited to current topology.
But still, I wanted to throw this out there and hopefully get a response from someone who's better informed.
I have now. I always have that nagging feeling...
But after MANY iterations, finally success. At least partly. 
BlinkWithoutDelay works AND mysensors sketch as well (will do more testing...).
What made it work, if anyone else struggles with this:
-connect uno (to computer-linux), board:uno, upload ArduinoISP, disconnect
-add shield to uno and atmega328p-pu to shield, connect to computer, board: "8mhz on breadboard", "programmer: "Arduino as ISP", burn bootloader, disconnect
-board: Uno, connect as above, "upload sketch using programmer", disconnect EDIT this last part appears to work but internal clock is all messed up. Bootloader works fine like this.
The magic happened after I changed the board back to Uno after burning bootloader. Why is beyond me, but maybe some arduino-ninja can figure it out.
@gohan N00b question, but which steps from the step-by-step need to be redone to "compile it" after altering myconfig.h? Or can you just post the command lines? 
Nevermind. Whined too soon.
Completely worked over the node4 code, moved "include"s around and eventually changed the relay presentations and receive clauses. Hope this helps someone with their problems later:
Thanks a millions!
void before()
{
// Set relay pin in output mode
pinMode(RELAY_1, OUTPUT);
// Set relay to last known state (using eeprom storage)
digitalWrite(RELAY_1, loadState(CHILD_ID_RELAY)?RELAY_ON:RELAY_OFF);
}
later this....
present(CHILD_ID_RELAY, S_BINARY);
....and ending with this...
void receive(const MyMessage &message)
{
if (message.type==V_STATUS) {
if (message.destination == MY_NODE_ID) { // Only switch the relay if the message is for this node
Serial.print("Updating relay state");
// Change relay state
digitalWrite(RELAY_1, message.getBool()?RELAY_ON:RELAY_OFF);
// Store state in eeprom
saveState(CHILD_ID_RELAY, message.getBool());
// Write some debug info
}
// Write some debug info
Serial.print("Incoming change for sensor:");
Serial.print(message.sensor);
Serial.print(", New status: ");
Serial.println(message.getBool());
}
}
@anticimex I've built a new node, DHT11 that sends temp&hum data. I reconfigured Rpi with this:
sudo ./configure --my-transport=nrf24 --my-rf24-irq-pin=15 --my-signing-debug --my-signing=password --my-signing-password=XXXXXX --my-gateway=mqtt --my-controller-ip-address=127.0.0.1 --my-mqtt-user=YYYY --my-mqtt-password=ZZZZZ --my-mqtt-publish-topic-prefix=mysensors-out --my-mqtt-subscribe-topic-prefix=mysensors-in --my-mqtt-client-id=mygateway1 --my-leds-err-pin=12 --my-leds-rx-pin=16 --my-leds-tx-pin=18
This is what I get in gw syslog:
Apr 2 22:53:11 DietPi mysgw: Starting gateway...
Apr 2 22:53:11 DietPi mysgw: Protocol version - 2.2.0
Apr 2 22:53:11 DietPi mysgw: MCO:BGN:INIT GW,CP=RNNGLSQX,VER=2.2.0
Apr 2 22:53:11 DietPi mysgw: !SGN:BND:PWD<8
Apr 2 22:53:11 DietPi mysgw: !SGN:INI:BND FAIL
Apr 2 22:53:11 DietPi mysgw: TSF:LRT:OK
Apr 2 22:53:11 DietPi mysgw: TSM:INIT
Apr 2 22:53:11 DietPi mysgw: TSF:WUR:MS=0
Apr 2 22:53:11 DietPi mysgw: TSM:INIT:TSP OK
Apr 2 22:53:11 DietPi mysgw: TSM:INIT:GW MODE
Apr 2 22:53:11 DietPi mysgw: TSM:READY:ID=0,PAR=0,DIS=0
Apr 2 22:53:11 DietPi mysgw: MCO:REG:NOT NEEDED
Apr 2 22:53:11 DietPi mysgw: MCO:BGN:STP
Apr 2 22:53:11 DietPi mysgw: MCO:BGN:INIT OK,TSP=1
Apr 2 22:53:11 DietPi mysgw: GWT:RMQ:MQTT RECONNECT
Apr 2 22:53:11 DietPi mysgw: connected to 127.0.0.1
Apr 2 22:53:11 DietPi mysgw: GWT:RMQ:MQTT CONNECTED
Apr 2 22:53:11 DietPi mysgw: GWT:TPS:TOPIC=mysensors-out/0/255/0/0/18,MSG SENT
Apr 2 22:53:23 DietPi mysgw: TSF:MSG:READ,99-99-255,s=255,c=3,t=7,pt=0,l=0,sg=0:
Apr 2 22:53:23 DietPi mysgw: TSF:MSG:BC
Apr 2 22:53:23 DietPi mysgw: TSF:MSG:FPAR REQ,ID=99
Apr 2 22:53:23 DietPi mysgw: TSF:PNG:SEND,TO=0
Apr 2 22:53:23 DietPi mysgw: TSF:CKU:OK
Apr 2 22:53:23 DietPi mysgw: TSF:MSG:GWL OK
Apr 2 22:53:23 DietPi mysgw: SGN:SKP:MSG CMD=3,TYPE=8
Apr 2 22:53:23 DietPi mysgw: TSF:MSG:SEND,0-0-99-99,s=255,c=3,t=8,pt=1,l=1,sg=0,ft=0,st=OK:0
Apr 2 22:53:25 DietPi mysgw: TSF:MSG:READ,99-99-0,s=255,c=3,t=24,pt=1,l=1,sg=0:1
Apr 2 22:53:25 DietPi mysgw: SGN:SKP:MSG CMD=3,TYPE=24
Apr 2 22:53:25 DietPi mysgw: TSF:MSG:PINGED,ID=99,HP=1
Apr 2 22:53:25 DietPi mysgw: SGN:SKP:MSG CMD=3,TYPE=25
Apr 2 22:53:25 DietPi mysgw: TSF:MSG:SEND,0-0-99-99,s=255,c=3,t=25,pt=1,l=1,sg=0,ft=0,st=OK:1
Apr 2 22:54:18 DietPi mysgw: TSF:MSG:READ,99-99-0,s=1,c=3,t=16,pt=0,l=0,sg=0:
Apr 2 22:54:18 DietPi mysgw: SGN:SKP:MSG CMD=3,TYPE=16
Apr 2 22:54:18 DietPi mysgw: !SGN:NCE:GEN
Apr 2 22:54:23 DietPi mysgw: TSF:MSG:READ,99-99-0,s=0,c=3,t=16,pt=0,l=0,sg=0:
Apr 2 22:54:23 DietPi mysgw: SGN:SKP:MSG CMD=3,TYPE=16
Apr 2 22:54:23 DietPi mysgw: !SGN:NCE:GEN
This is kicking my butt... I cant understand that last part about the nonce 
I will add the code from the node as soon as possible.
Just a quick idea: are you powering the RFM69 from the Rpi?
I use a Rpi Zero W and when I powered my radio NRF24 from that it doesnt get enough juice even with caps.
I now use a bigger USB-wall wart and use AMS1117-3.3 to power the radio (PA-version) and added caps.
My two cents
@mfalkvidd Made the password 10 characters. From looks of the logs, it's working now.
I cant believe I skipped the step of making the password longer... Just got too fixated on the password I came up with.
Apparently sleeping less and debugging late solves problems. This is SOLVED.
My IDE library was outdated. I updated my Arduino Mysensors-library, upload to one node, and my node started to communicate fine. Must reupload all nodes unfortunately. Probably the problems are caused by signing differences in previous library versions vs. 2.3.0 release for Raspberry.
Again, hope this helps someone who encounters the same problem.
@ej3-martin My LEDs come on when the Rpi boots (is that what you mean by testing?). Also you can invert the LEDs (on but blink off) if you want. I figured the wiring makes for better power delivery rather than feeding voltage from the GPIO
@rozpruwacz Got lucky and found an extra W5100 without the 100ohm resistors. Also disabled the static ip (I set it from the routers ip table instead).
Now, it seems the gw is breathing..
I had weird problems as well. My W5100 module was at fault.
One module needed resistors and one didn't. I never figured out the problem. I also had what seemed a good ethernet but weird connection problems.
Check this thread out, just in case it helps.
https://forum.arduino.cc/index.php?topic=351477.msg3215306#msg3215306
I dont know what controller you are using but I had similar problems with domoticz when presenting s_light_level and V_Level vs v_light_level. It had to do with domoticz update.
Thats what came to mind. I didnt find a sketch problem if this wasn't part of your problem.