How are agencies handling visual regression testing across client sites?

We manage around 20 client sites and lately the annoying part has been catching small visual issues after WordPress or plugin updates. Usually it's something minor like a section shifting, a form looking off, or mobile spacing getting messed up, but we don't always notice until the client does.

Looking into visual regression testing mainly so we're not manually checking every important page after updates. What are other agencies using for this?