Hi there,
I don’t know the answer yet to the change in SSH but Gitlab provides the links to show you how to clone a repository using HTTPS instead of SSH on the top-right of each project page:
I just tried this for a repo that I own and clone/push/pull worked perfectly fine using HTTPS.
For repositories you haven’t yet cloned simply use the HTTPS url when you perform clone.
For repositories you previously cloned you’ll need to open the (hidden) file .git/config within the project and replace-all git@gitlab.pavlovia.org: with https://gitlab.pavlovia.org/ (or fetch the url from the gitlab site and do it one-by-one).
hope that helps but I’ll also post here if I find out why SSH authentication has changed
best wishes
Jon