User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) snap Chromium/77.0.3865.90 Chrome/77.0.3865.90 Safari/537.36
Steps to reproduce:
This bug was initially reported against the thunderbird 68.1.1 package in Ubuntu (https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1847247).
Thunderbird 68 is not able to make use of external hunspell dictionaries provided by the distribution in /usr/lib/thunderbird/dictionaries.
This is a regression compared to thunderbird 60.9.0 and earlier, which locates and uses hunspell dictionaries installed in /usr/lib/thunderbird/dictionaries.
As far as I can tell, other distributions (such as Fedora 30) are similarly affected.
It looks like https://hg.mozilla.org/mozilla-unified/rev/8810007550b1fdeeae0f5d797c4a511818a57be7 is the revision that removed this ability. The tracking bug with the rationale is https://bugzilla.mozilla.org/show_bug.cgi?id=1457321, but it doesn't mention anywhere the way Linux distributions install external hunspell dictionaries and make them available to thunderbird. I wonder whether this was an oversight, or whether that use case was indeed considered but deemed unimportant when compared to the performance improvements that this change brought.
Either way, would it be possible to consider adding back the ability to load external dictionaries from the file system, maybe behind a setting that would be off by default?