People still can install/run whatever they like on their PCs, so why further restrictions needed or am I missing something? Also, further restrictions doesn't seem to work on the mobile/TV market where actual malware still infects iOS/Android/TV devices despite all the "hops" that it has too go through.

Code signing with warnings about non-signed apps is enough

Hmm? Malware on iOS is extremely rare.

I remember in Bitcoin community ~10 years ago, standard recommendation was than an iOS wallet was secure enough (I don't recall even a single case where wallet was stolen via malware), but any private keys on Windows were strongly discouraged, as most cases of stolen wallets were on Windows.

I'd say popularity of iPhone shows which way people prefer, but you do you - what prevents you from voting with your wallet and buying a Linux phone?..