arm is the nicest instruction encoding you can get actual hardware for (not thumb or aarch64). risc-v is pretty okay at the assembly level but the instruction encoding is almost deliberately sadistic. amd64 isn't too terrible but not nearly as nice as arm

older official arm documentation is a lot better than recent, which is very poor quality (though still pretty reliable.) oldnewthing and azeria-labs have good tutorials, though she got some of the condition flags wrong