Hello! I'm the usptream maintainer of Deja Dup. I was recently made aware that Google will be removing an oauth workflow that Deja Dup uses in September. This means that any new authentications for users trying to connect Deja Dup to their Google account will fail after that date (existing users that have already authenticated themselves will continue to work). If possible, updating to 43.3 will fix this. But for older releases, I recommend a backported patch. Here's a wiki page for more information about the issue, including backported patches for older versions: https://wiki.gnome.org/Apps/DejaDup/GoogleAuthChange2022
Thanks for the heads up!