User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0

Steps to reproduce:

1. Upgrade server from RHEL 7 to RHEL 8
2. Start thunderbird

Actual results:

Thunderbird shows me the "You have launched an older version of Thunderbird" dialog:
"A newer version of Thunderbirder may have made changes to your profile which are no longer compatible..."

Expected results:

Thunderbird should have started.

The upgrade was from thunderbird-68.9.0-1.el7.centos.x86_64 to thunderbird-68.9.0-1.el8_2.x86_64 so I fail to understand what the issue is.

If I force thunderbird to start with --allow-downgrade it gets up and running, but the account doesn't work. So something is amiss.

Exactly what is thunderbird looking at to determine the profile version?

Alright, so I found "compatibility.ini", and it states:

[Compatibility]
LastVersion=68.9.0_20200619122635/20200619122635
LastOSABI=Linux_x86_64-gcc3
LastPlatformDir=/usr/lib64/thunderbird
LastAppDir=/usr/lib64/thunderbird

The date there seems to match the build date of the RHEL 7 RPM. And the RHEL 8 RPM is actually built a few days earlier (2020-06-05).

Is thunderbird that picky that it will refuse even this upgrade?

And does this mean that should be safe to run --allow-downgrade and the subsequent issue I'm having there is something else?

For reference, the serious bug I'm seeing is bug 1651629 and bug 1651640. --allow-downgrade or removing compatibility.ini is sufficent workaround for the bug here.

So this is a duplicate of Bug 165629. Is that what you are saying?

No. I was seeing several fairly unrelated bugs, and it was bug 1651629 that was giving me the most trouble and not this one. When filing this bug I wasn't sure if there were several bugs at play or just this one.