AdGuard for Safari is free and well respected. (And GPL3, if that floats your boat.) https://github.com/AdguardTeam/AdGuardForSafari

1Blocker is also well respected, but not free.

If uBlock Origin is a hard requirement, Firefox is available for the Mac.

You might wanna take a look at Orion browser by Kagi. Built on WebKit like Safari, but not open-source (yet, as they say). The interesting part is that it supports addons from both Chrome and FF.

I'm fairly sure AdGuard works fine on Safari, though I have heard its performance is lacking -- shame, as Safari is a great little browser (despite my personal dislike for macOS).