I just priced laser projection keyboards. 40.00 or so. I think that’s the ”safest” option.

Presuming you have sufficient levels of assurance that no software exploits are present and no keystroke loggers etc. The only way to attack and the value of the attack being high enough (root CA compromise?) that an adversary would deploy (laser) mics.

I figure that anyone this concerned would program a coupe of rubber duckies or yubikey static mode ? Then the emitted strings would be unknown.

Also what about collecting from the screen via emissions?