There is no mention of sync functionality. I regularly use 3 different PCs and I cannot sync settings easily. It means I've give up using Thunderbird on all but one of the PCs.
They've also made the usability worse in recent versions and are copying the insanely annoying context menus in Windows 11, which cannot be reverted.
You need to export the profile and re-import on each machine. If you make any changes on one machine you want to see it reflected on the others.
The profile import is a bit iffy and there was some odd issues with downloading profiles over 2GB IIRC, the last time I did it (which was over 2 years ago).
There seems to be a lot of focus on features that IMO that I couldn't care less about and some outright stupid UI decisions like the context menus being changed after 20 years for god knows what reasons.
The result was that I just gave up and use Thunderbird on one machine and web-mail on all the others. I suspect I will just drop Thunderbird as a result.
I guess they mean that they want their accounts to be synced (setup is annoying tbh), but also things like signatures and so on.
I normally just manage it myself and I'm extremely happy to do so, as I consider it like my dotfiles, but I understand where the parent is coming from - settings sync is becoming common. (Chrome is a good example).
Also gave up Thunderbird years ago because of the same reason. Just wanted something stable and chose Spark. Works on every device, not a problem for years.
They've also made the usability worse in recent versions and are copying the insanely annoying context menus in Windows 11, which cannot be reverted.