It was hard to choose where to post this unusual issue that I doubt many people have noticed. Yesterday, June 5, I could no longer access my gmail account in Thunderbird. After deleting the account and trying to enter it again, I found that Thunderbird could no longer even query the gmail server to determine settings to create the account. It didn't matter what gmail account I tried it with. There was no problem with other servers. Only gmail. It so happens that I had Sparky 6 installed on 3 different PCs with completely different hardware. (It should be noted that I use Sparky 6 Semi-Rolling, with the Sid repo enabled.) Same situation on all 3. These PCs are all multi-booting 2 or 3 different Debian and Ubuntu based distros, including Debian, Mint, Siduction, MXLinux, and Ubuntu-Cinnamon Remix. (I test a lot of distros side by side.) All of them, including Sparky are running the Cinnamon Desktop. There was no problem on any of the other distros. Only Sparky. I know exactly what had occurred in system updates just before this happened, and I don't think it's a coincidence. Mozilla's Firefox 89 had just become available on the Debian servers the day before. This problem started on Sparky after the update that pulled Firefox 89 and downgraded it back to 88.01. This same downgrade occurred on Debian and Siduction, but Thunderbird still worked with gmail on those distros. The Ubuntu-based distros haven't pulled Firefox 89 from the repos, and no problem occurred on those. When trying to set up a gmail account in Thunderbird on Sparky, I get an error message from the gmail server about security features not meeting their standards. Needs looking in to.
Check to make sure the setting is still enabled for your gmail account(s) by logging in via a browser.
I am presently using T'bird 78.10.0 on a bullseye machine with gmail accounts.
If you download the bz2 file from Tbird direct you will then have a self contained version which should avoid any possible breakage by files imported through sid.
Thanks for the info. I'll be looking into it.