So, it looks like the SAFE UI does not show BASE safes anymore? 
What alternate UI should I use in the meantime?

I tried using https://eternalsafe.eth.limo/ for my optimism safe with... some amount of success.

https://app.onchainden.com/ worked a bit better for me. Fun time to try the alternatives!

Unlock Protocol founder.
Previously founder at Superfeedr (RSS push API) acquired by Medium!

https://ouvre-boite.com

Head of Growth at @palmera | @dragonstake | Co-Founder at Crypto Plaza, Spanish speaking community. 

Palmera allows web3 organizations to manage safes, integrations, automations, and credentials in one place. Backed by @safe and @longhashVC

Maybe you can try also Palmera. You can ask Marcela.
@mircala 
@palmera