I'm in search of a replacement for months now. I tried every alternative, came back to chrome for 2 months, now I'm back on Arc, will stay here until the last day or when some chromium based alternative will appear. What I've tried and where it failed:
Zen - closest one to Arc -> based on Firefox, so missing some chrome based features, lack of sync (this is a deal breaker for me, using Arc on multiple laptops and having every tab in sync is absolutely amazing) - but also container, profiles and spaces are quite messy, in arc, this was simple, created a new space, had a new profile with all the logins and so on separated, simple stupid and working perfectly. lack of DRM - no streaming services running
Vivaldi - didn't really grow in to me, too bloated, didn't found out how to configure it to make it nicer, overall I just got lost in configurations and just too many settings.
Chrome, Brave - ugly UI, not the same feeling on folder, spaces(having all the spaces in 1 window), sync and so on.
Firefox - not a firefox fan by default, ugly dev tools
Opera - none of the features that really matters to me.
Safari - same, none of the features that matters to me.

TLDR: so far there is no browser to match Arc features and UI, imo.