I'll second EinkBro as an awesome browser. I absolutely cannot stand anything else on my e-book reader: Onyx BOOX Max Lumi, Firefox/Android, Onyx's NeoBrowser (rebranded Chromium), and DDG Privacy Browser installed, I only use those if EinkBro blows up for some reason, which it very rarely does.
I've had a lot of interactions with the developer and the GitHub repo, and he's been quite responsive. Hasn't addressed everything, but several features added and bugs get smashed fast.