After couple of days in EasyEDA, I've got this which is now in production.

Parts are hopefully to arrive roughly when boards do and so assembly waits for a later day, probably next year because non-building stuff does get in the way and I'm not even sure what the blackout situation will look like in a week - lights are already off twice or thrice during the day for several hours after missile attacks on our energy infrastructure.

Schematic mostly repeats part of Radiomaster TX16 reverse effort, check them out, plenty of info, and now after boards are on the way I kind of think I'm sleepwalking into a disaster - there is a high chance that tristate switches are not actual two switches but rather a voltage divider sampled by ADC, whereas my implementation uses a ton of switches hooked up to IO expander in a matrix fashion.

We'll see I guess.