Firefox 83.0 snap was* broken (fixed square fonts)

Glad you found a workaround for the problem Eduardo.

You are right, this issue is concerning and should definitely not happen when the snap is being updated without user intervention. I wonder whether this was caused by the snap being refreshed while it was running? If so, that would be yet another symptom of bug #1616650, which can be mitigated by turning on the Refresh App Awareness experimental feature.

In any case, let’s keep this thread open, in case others stumble upon the same problem.