HotA is awesome!
But the best way to play it is to use VCMI. It’s an open source re-implementation of the original game for the modern hardware. It also have a built-in launcher which asks you automatically download HotA or WoG after the first start. You can also install other mods from it. So convenient.
SMS is even worse in terms of openness. You won’t find a modem that runs open source baseband firmware. It’s because the radios are subject to several regulations which means customers can’t be able to modify that firmware.