Floorp Flatpak, or one.ablaze.floorp, now should be able to function with Plasma Browser Integration - afaik the only thing stopping it from doing so now is it not being whitelisted in the client-side process itself. I plan on adding it to the whitelist once I have an opportunity to test it works, but I'm filling this 'bug' to make it known and give any Merge Requests to whitelist Floorp a bug report to link to.