Ultima VII Part 2: Serpent Isle and its expansion The Silver Seed are available for download at GROG!
Serpent Isle is a better but more linear story than
The Black Gate. The gameplay in
Serpent Isle is also very linear and structured. NPC party members and all subplots are integral into the main storyline.
Serpent Isle is less of a RPG and closer to being an adventure game. IMO,
Ultima VII Part 2: Serpent Isle has the best storyline, the best characterization, and the best pacing in the entire classic series. (I have play through
Ultima IV to IX, including both
Underworld games and both
Worlds of Ultima games.)
Exult supposingly is an open source project to update the
Ultima VII game engine. However,
Exult website indicates that the project is completed but the project does not update the entire engines, 100%. For example, hit points and damages do not work properly in
Exult, and animals can open doors.
Exults have quite a number of known issues, big and small. It does not seem that
Exults will release newer versions to deal with those issues. So, I can't recommend using
Exult to play
Ultima VII.