Firefox has rolled out "Total Cookie Protection" starting with v101.0.1.

"Total Cookie Protection works by creating a separate “cookie jar” for each website you visit. Instead of allowing trackers to link up your behavior on multiple sites, they just get to see behavior on individual sites...No other websites can reach into cookie jars that don’t belong to them and find out what the other websites’ cookies know about you..."

Read more at the Mozilla blog here.

I presume this is automatically enabled without having to change settings manually since I don't see any TCP options on Firefox's Tools>Settings>Privacy&Security screen. But you might want to enable "Delete cookies and site data when Firefox is closed" on that screen, if it's not already enabled.