Ok comparing the three machines :
⋅ A B C : Gimp as snap can’t access ~/.local/share/fonts ( regular folder, not link ) but do access ~/.fonts ( which by default does not exist ).
⋅ A B C : if I put inside ~/.fonts links to my folder of fonts on another disc, they will be available in Gimp-snap
⋅ BUT, there’s a but, on A and B as soon as I do that ↑ launching of gimp halts 30~40 on the « fonts » loading.
⋅ so now I have to find what’s different on machine C ( where fonts are linked and launching of gimp is normal )
Mmm… on machine C, I did not bind my extra folder of fonts through fstab inside /usr/share/fonts/EXTRAS because there is only one disc inside and only one partition on that disc.
The 30~40s halting may come from Gimp seeing twice the same fonts ( once through the bind in /usr/share/fonts/EXTRAS and another once in ~/fonts/link which actually both target the same resource ).
So, what remains to confirm ?
Are you sure gimp-snap can access ~/.local/share/fonts ?
And if so why on my three installations ( all Ubuntu 20.04 ) Gimp-snap
⋅ shows permission denied if trying to browse ~/.local/share/fonts
⋅ is fine with ~/.fonts which is not there by default.