As others have commented, the Ultima games (at least, many of them) run in DosBox. GOG has Linux installers for other games that use DosBox. Given that the hard work of DosBox/Ultima configuration has already been done, it would seem like the work of an afternoon to provide official GOG installers for all of the Ultima games that use DosBox.

I know that it is possible to use Wine to install the GOG Windows versions and then manually configure my own DosBox to play the resulting directory. But native Linux installers would be IMMENSELY more convenient.

(as would a Linux Galaxy client, but that's a totally separate topic)