I've been using a non add-on store addon for this.. and no idea why something basic like that would not be in the core or this add-on
https://addons.mozilla.org/en-GB/firefox/addon/containerise/
I'd have every tld on it's own profile and allow creating groups that merge profiles if needed.
It's a bit tedious to set it up at first but it's the only way I know of to get the following functionality:
With GMail open in a "google" container, non-google domain links open in non-google containers (configurable which container if any). Google domain links (drive, calendar, maps, etc) open in the google container.
Once setup, this means in your "standard" or non-specified container you can log out of all google services and stop their most explicit tracking of you through simple account cookies being read across the web while you search, etc. No longer when you visit sites that allow sign-in with google will your account name be auto-suggested, because the sites don't have that level of tracking info when you're browsing and searching outside of the google container. Viewing random trash yt videos will no longer sway the recs you get in yt.
The downside is that my google searches, done outside the google gulag, run into captcha prompts b/c I guess google search doesn't expect that much consistent traffic from someone who isn't signed into one of their services.
edit: this also means that you can, for example, containerize gmaps and set it up so that non-google domain links followed out of maps open in a non-google container. clicking a link to a business's website from their gmaps page no longers propagates your google account cookie to their site, etc. it opens in a different container, automatically.