Maybe some of the commenters here could help me out. In terms of routes that are east to ride a loop from the car without a shuttle in the area, MDO and Irish in SLO come to mind, as well as Ehlings Park and Jesusita in SB. Are there others that I’m missing?
Can you define easy [east]? Terrain or logistics? No out/back?
Disclaimer: I'm no SB expert so maybe someone can elaborate/correct
You can do various loops based on the Romero climb. I like Romero to Cold Spring, but it requires a little (pleasant) road riding to start if you park at the bottom of CS. Not necessarily an easy ride, but it's great IMO.
Romero FR to ST, Romero to San Ysidro, etc. I believe there are numerous shorter loops that connect to the lower parts of these trails among others. Edison trail comes to mind. I'd imagine there are a few loop options around Jesusita/Tunnel but I'm not very familiar with that area.
I believe the backcountry SB trails are now open/rideable after fires, so something like a Santa Cruz trail might be an option.
I'm a big fan of Cuesta loops starting at Stenner.