I use it on Linux Mint, the biggest issue I have with it is external links:

github.com/linuxmint/webapp-manager#how-to-open-l…

How to open links in my main browser?

For Firefox, all links are always opened within the WebApp, either directly or using a new tab. To open a link in your main browser, right-click anywhere, select Copy link location and paste the link in your main browser.

Really annoying. PWAs For Firefox fixes it, you just gotta change a setting.