+1 for having a native linux client. I'm not sure what the process would be, but being electron based I can't imagine it being extremely hard. Right now I'm using https://github.com/sysdrum/notion-app to basically wrap a browser instance. But there's a very noticeable performance difference between this hacky solution and my friends native electron client on MacOS. Especially on my heavier pages with lots of photos. Notion has completely changed my life and workflow, but I feel like I'm starting to run up against the limits of what I can do on the operating system I'm on. I even considered reaching out to CodeWeavers the makers of Crossover to see what it would take to make a linux port, but it seems like I actually have to be the owner of the app being ported for that to be an option.
I haven't tried it in firefox, I'll definitely give it a look. Using it in chrome however, the performance feels the same as the hacky electron wrapped version. I notice it the most when switching between two heavy pages or trying to get to the bottom of a page I have 50+ pictures saved to. But it's useful for me to still have it register as a separate application in case I ever need to kill chrome for some reason. Or for organizing it across my different desktops.