At minimum, i do not expect backdoor designed to steal Bitcoin on such general electronic board/module.
That's quite an assumption. I'd prefer a much more generic air-gapped laptop with a throughly tested Linux distribution and Bitcoin Core (or Electrum).
I don't need anything that isn't moving money from A to B in a legacy address, any other "features" added after that just add complexity and potential exploits, as well as nonsense usages of block space like ordinals and co.
I don't want Ordinals (spam) either, but as long as it's using Bitcoin blocks, your node will have to verify them.
Let's just hope no fatal bug is added along the way
Let's assume you switch to much less popular and much less tested software that offers less features than Bitcoin Core. What makes you think that software is less likely to have bugs?