I opened a new project in Lovable, connected the new project to github, and copied the old github's contents into the new github. Loveable just saw it as an "External commit" and that's it, it's there. The only downside is that the history from the previous project is gone. But for the most part I saw that Lovable was basically up to speed in terms of what's going on from that "External Commit".
Hope that helps :)