This isn't a question about the "Multi-Account Containers" addons, I am pretty sure that there was a section called "Container tabs" in the privacy and security settings, and I could use containers without installing an addon some days ago. I can still access by directly viewing this address about:preferences#containers But I can't find it in the settings, and this feature does no longer work. So I went to read recent release notes from Firefox 100 to 101.0.1, but I didn't find any notes to say this feature has been disabled. Could this be an unexpected result of an update?