Regarding the snap. My canberra-gtk-module was fine and I was able to get the snap to run by installing it using:
sudo snap install --dangerous --devmode /home/kurtm/Downloads/GravitDesigner/gravit-designer_3.2.6_amd64.snap
I had to run it unconfined. All of the other snaps that I’ve used have installed and run fine without requiring unconfined access, so I’m wondering if your snap is missing some libraries.
After getting Gravit to run in snap form, the snap ran fine, including selecting the system fonts option, however, it only displayed the 6 fonts included in the snap, and 3.25 works fine with way more than 6 system fonts. Since the snap did not access my actual local fonts, it really didn’t resolve any questions. That said, I like the idea of a snap or flatpack that can be installed and managed using built in Linux applications management.
I don’t have an answer to the issue, but I think that I have some clues both from the error log and observation. I believe that rather than the number of fonts directly causing the lockup, I suspect that there are parallel processes running and that a large number of fonts sometimes results in the canvas draw process starting prior to the point that the font list has been fully parsed. I suspect that if you build the system font list at application load time, rather than waiting until the system fonts dialog is clicked, the issue might be mitigated. I suspect that Gravit is actually running on Chromium and there seem to be several issues related to the errors in my log:
Nov 23 02:46:45 t110.river.lcl appimagekit-gravit-designer.desktop: [10469:1123/024645.442539:ERROR:gles2_cmd_decoder.cc(17518)] [.RenderWorker-0x37dff937c00]GL ERROR :GL_INVALID_OPERATION : glBindTexImage2DCHROMIUM: no image found with the given ID
Nov 23 02:46:45 t110.river.lcl appimagekit-gravit-designer.desktop: [10469:1123/024645.442624:ERROR:gles2_cmd_decoder.cc(16743)] [.RenderWorker-0x37dff937c00]GL ERROR :GL_INVALID_VALUE : glCopySubTextureCHROMIUM: source texture has no data for level
Some of these issues seem to relate to hardware accelerated drawing of the canvas, which could be hardware specific.
The above is speculation, but I can’t identify any way to resolve the issue other than deleting a bunch of fonts.