Side channel attacks shouldn't be your main concern, secp256k1 libraries has mitigations against most of that so you'll be mostly safe.
Sorry, I was meaning trivial side channel attacks like someone looking over your shoulder and you not taking care because it's only testnet. But I see now it's a bad idea, better separate main and test.
Problem would be with [...] some $5 wrench attack.
That's unfortunately true, but what to do if you have a nomadic lifestyle in those difficult times? I would prefer a geographically distributed multisig setup, but that's not possible because I can't be sure if I can enter my country again in a few months with shit going more crazy every day.
it's quite dangerous for people to be memorizing seeds.
Why?