From the Downloads page:

> Updating KeeperFX will often break your saves. If you don't want to lose progress, it's suggested to complete your games before updating.

That’s… unfortunate.

Repo: https://github.com/dkfans/keeperfx

It’s unfortunate that this is Wintel only.

> KeeperFX is a standalone game but requires a copy of the original game files as proof of ownership.

Darn it.