Hello @pragtich,
Thank you so much for your reply. Your tips on how to debug serial port and GPIOs were extremely helpful.
Thanks to that I have found the reason it was not working. It was poorly soldered pin of bidirectional level shifter (the one for the driver enable pin).
You've pointed me in the right direction.

I will leave some information about my configuration and wiring, if someone would try the same thing.
Here is the pinout for NanoPi NEO.

Pin PA1 on the board can be configured with --my-rs485-de-pin=1.
Pin PG11 on the board can be configured with --my-rs485-de-pin=203.
See section 4.1. of board documentation to see more.

I use MAX485 module for RS485 and all wires for it (TX, RX, DE) are going through bi-directional level shifter (3.3V <-> 5V).
I am running Armbian 20.11 Bionic with Linux 5.8.16-sunxi on NanoPi NEO. I've tried latest one, but had some problems with accessing ports.

Hello,
I would like to ask if anyone has successfully run Gateway on NanoPi NEO with Armbian installed.
I am especially interested in running it with RS485 as a transport, but any information will be helpful.

I have successfully compiled and run MySensors on the NanoPi Neo:

$ ./configure --my-transport=rs485 --my-rs485-serial-port=/dev/ttyS1 --my-rs485-de-pin=1 --my-gateway=mqtt --my-controller-ip-address=192.168.1.100 --my-mqtt-publish-topic-prefix=mysensors-out --my-mqtt-subscribe-topic-prefix=mysensors-in --my-mqtt-client-id=mygateway1
[...]

$ make
[...]

$ sudo ./bin/mysgw

Jul 28 00:18:53 INFO  Starting gateway...
Jul 28 00:18:53 INFO  Protocol version - 2.3.2
Jul 28 00:18:53 DEBUG MCO:BGN:INIT GW,CP=RSNGL---,FQ=NA,REL=255,VER=2.3.2
Jul 28 00:18:53 DEBUG TSF:LRT:OK
Jul 28 00:18:53 DEBUG TSM:INIT
Jul 28 00:18:53 DEBUG TSF:WUR:MS=0
Jul 28 00:18:53 DEBUG Serial port /dev/ttyS1 (9600 baud) created
Jul 28 00:18:53 DEBUG TSM:INIT:TSP OK
Jul 28 00:18:53 DEBUG TSM:INIT:GW MODE
Jul 28 00:18:53 DEBUG TSM:READY:ID=0,PAR=0,DIS=0
Jul 28 00:18:53 DEBUG MCO:REG:NOT NEEDED
Jul 28 00:18:53 DEBUG MCO:BGN:STP
Jul 28 00:18:53 DEBUG MCO:BGN:INIT OK,TSP=1
Jul 28 00:18:53 DEBUG GWT:RMQ:CONNECTING...
Jul 28 00:18:53 DEBUG connected to 192.168.1.100
Jul 28 00:18:53 DEBUG GWT:RMQ:OK
Jul 28 00:18:53 DEBUG GWT:TPS:TOPIC=mysensors-out/0/255/0/0/18,MSG SENT
Jul 28 00:18:53 DEBUG TSM:READY:NWD REQ
Jul 28 00:18:53 DEBUG ?TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK:

I have the node with BME280 prepared and I've tested it works correctly with another gateway (Arduino Mega).
All wires triple checked and I am running out of ideas.
Any tips are highly appreciated.
Knowing this setup works for someone else will be already a huge help.