Only possible if all handheld machines have transparent hardware designs, i.e., all electronic components inside are known, have open source drivers and do not rely on third-party proprietary drivers or reverse engineering. This is due to Linux itself rely heavily on open source software and doesn’t play well with proprietary parts (take Nvidia GPU for example, every person who has it in their Linux machine knows it causes headache once in a while). Unfortunately, so far only Valve’s Steam Deck has a hardware specs that satisfy this requirement. The other ones more or less suffer from closed source components