There is nothing you can do to make Firefox or Chrome to understand what a “federated network” even is. For a browser, an “Origin” is an extremely well defined concept. You can’t just decide to amend it because that’s how you feel it ought to be. If you can’t make mastodon.social be relates to social.mastodon in the browser, then you’ll have a rough edge. And that’s just to start. Federated services have so, so so so, many usability issues that all could be attributed to what a “browser” interrupts HTTP or the internet to be vs what is actually possible.