"Offer your servants" is offered unconditionally at all slave guilds, usually as the second button (it can move down if options for side quests are listed above). It is unaffected by game mode or slave count; you can sell the starting slave, though that's generally not a good idea.
Do you have any mods installed? That is the only thing I can think of which would cause that to change as it has been that way for several years.
The game is quite stable, but now and again we see unique problems with specific computers. In the appdata is a folder for logs (on Windows, %appdata%/Strive/logs)(Edit: if you installed through the itch.io app, it may be in a weird location and be easiest to open it in-game through the mod menu's "Open Mod Folder"). The godot file should list any errors that occurred (edit: updated when program closes), though the last 8 lines will be normal errors related to closing the game. However, as of version 1.0d the game no longer runs in debug mode and most errors end up crashing the game instantly, so I have doubts that it will show anything useful. Especially since it is very unlikely that only that button would missing, rather if there was a problem the slave guild would either not show up or behave as a softlock.
