To clarify and get this off ZRT. For a short while in 2020, Xiphos was
dropped from Debian testing because of
debbug#947542. Unfortunately, at that time Ubuntu was last synced to Debian before release of Focal (20.04). Thus, Xiphos got removed from Ubuntu 20.04, and consequently, from Linux Mint 20.x. It can be installed from the
CrossWire PPA.