Logged into one of my characters today and I got a popup window that said, "SUI is not being actively developed at the moment. Consider switching over to mUI (very similar to SUI) for future updates and support." , then gives a curseforge address to the addon.
Anything to this?

Yes. SUI is not receiving any updates at the moment as Syiana is busy irl for quite some years already, and I created mUI which I actively maintain.

Appreciate the quick response; thanks for the info. Wasn't sure what was going on. I'll switch over.