I think ~/.fonts should also be exposed when using the new desktop interface. You will need a more recent libreoffice snap than the one currently in the candidate channel, as I recently added the desktop interface and didn't publish anything yet. I'm working on an update that I hope will go to the candidate channel later this week, so keep an eye out for it, and test again when the call for testing is out.
I think ~/.fonts should also be exposed when using the new desktop interface. You will need a more recent libreoffice snap than the one currently in the candidate channel, as I recently added the desktop interface and didn't publish anything yet. I'm working on an update that I hope will go to the candidate channel later this week, so keep an eye out for it, and test again when the call for testing is out.