[$] Producing an application for both desktop and mobile

These days applications are generally moving away from the desktop and
toward the
mobile space. But taking a multi-platform desktop application and adding
two mobile platforms into the mix is difficult to do, as Dirk Hohndel
described in
his linux.conf.au
2019 talk. Hohndel maintains the Subsurface dive log application,
which has
added mobile support over the past few years; he wanted to explain the process
that the project went through to support all of those platforms.
As the subtitle of the talk, 'Developing for multiple platforms without
losing your mind', indicates, it is a hard problem to solve sanely.