Now I'm getting somewhere.
After I restart odroid, nodered works ok in browser.
Also, there are those error messages in syslog.
Then, under root, I run node-red-stop.
Error messages stop appearing in syslog !(great)
But, node-red still works in browser!
So I checked processes and there is this one:
3558 odroid 20 0 5204692 150944 39896 S 1.3 4.0 0:22.75 node-red
So apparently, i'm somehow running node-red process that works fine.
However I'm also trying to run node-red-rpi via node-red-start (?) command or using this service:
So now my question is, how do I find a place, where node-red process is set to start after reboot?
Also, if I simply delete this /lib/systemd/system/nodered.service I should make system stop looking for node-red-rpi (hence the error message in syslog should stop occuring).