I'd love to get away from Chromium based browsers. At the moment I am using Brave.

Is there any other browser that works on and syncs between: MacOS, iPhone / iPad AND Windows? It also has to have adblock capabilities on all of the devices. FireFox with uBlock Origin would be my first choice but afaik you can't block ads on iPad / iPhone on it.

Any recommendations?

Jokes on you. I've never used Chrome (outside of work limitations). I always liked the way Firefox looked over Chrome so never really got into it. I do use Edge Chromium every so often since some pages work better, but not sure if this would apply or not.

Also, does anyone know about the Duckduckgo beta browser, specifically what engine it uses? I tried it on a couple pages, but it seems pretty buggy right now.

I've played around with a few browsers, and while Firefox is a better alternative to chrome, I'd more recommend a privacy hardened fork of firefox such as LibreWolf or GNU IceCat. I've also used mullvad browser which is kinda neat.

Some people are too comfortable using chrome for it's extension library however, so if a mozilla-based browser doesn't fulfill the extensions requirement, Brave browser is a good choice. I haven't tried de-googled chromium, but I imagine it's food for the reasons it says on the tin.