Ubuntu Focal Fossa is the development version of Ubuntu which will become Ubuntu 20.04 later in April. Today, a change to libpango in Ubuntu means that the currently released Minecraft.deb no longer installs. Looks like a dependency needs fixing in the build of the Minecraft launcher deb.

$ sudo apt install ./Minecraft.deb
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'minecraft-launcher' instead of './Minecraft.deb'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
minecraft-launcher : Depends: libpango1.0-0 (>= 1.14.0) but it is not installable
E: Unable to correct problems, you have held broken packages.