There are browser extensions to read Epub for both Chromium-based and Firefox browsers. I’m not too crazy about the ones I’ve tried, but they do mostly work. There’s also something like Qread, which can handle the format. I think there is an add-on for MS Word as well.

Thorium Reader is the best tool that I've found for reading EPUB documents.

https://www.edrlab.org/software/thorium-reader/