I encountered the same problem upgrading from (jessie to) stretch to
buster today. I was successful using the simpler workaround of deleting
compatibility.ini from my profile. Once Firefox started, it recreated a
new compatibility.ini file automatically. Here is a comparison of the
old and new files:
ota@alfriston:~$ diff
~/.mozilla/firefox/bhojq6pr.default/compatibility.ini
~/firefox-pre-buster-profile/compatibility.ini
2c2
< LastVersion=68.3.0_20191203235607/20191203235607
---
> LastVersion=68.3.0_20191204133900/20191204133900
ota@alfriston:~$ firefox --version
Mozilla Firefox 68.3.0esr
ota@alfriston:~$ cat /etc/debian_version
10.2
ota@alfriston:~$ dpkg -l | grep firefox
ii firefox-esr 68.3.0esr-1~deb10u1
amd64Mozilla Firefox web browser - Extended Support
Release (ESR)
ota@alfriston:~$ cat /etc/debian_version
10.2
So this minor versioning glitch appears to explain the problem as
described above. I also found the Mozilla bug(s) from July that
addresses a similar problem, but which apparently doesn't handle this case.
https://bugzilla.mozilla.org/show_bug.cgi?id=1554029
https://bugzilla.mozilla.org/show_bug.cgi?id=1568252
HtH,
Ted
