

Just to play devil’s advocate. There was recently an unverified report that some inverters contained an undocumented cellular modem. If true, it could, in theory, allow for remote modification or control, even when fully “offline” as far as the client was concerned. Basically a mobile phone based back door.
The solution is better verification, rather than bans however. Grid scale devices should have the hardware randomly audited. The software should also be audited and check summed. This would be burdensome at domestic levels, but seems reasonable at grid levels.
Something like the allwinner A13 is down at the low end of practical. It’s about $1 per chip, wholesale. People have gotten it running on an ATMEGA before. It required a bunch of helper components however, and took 2 hours to boot up.