Interesting. I’m using IMAP. The weird thing is that I initially had no problems. Everything just stopped working all of a sudden. I got the information about checking the less secure apps box from doing some searching, and so far that’s the only thing that seems to have worked, at least on Evolution. It hasn’t made any difference at all in Thunderbird.
edit: I just unchecked the box in settings, in my browser, and now Evolution is back to not being able to log in. So, there’s definitely an issue there. It’s just that for some odd reason Thunderbird isn’t able to log in no matter what. I’ve been using Thunderbird with gmail for years without any issues, and as of a few days ago, it was still working. I have no idea what went wrong.