The Temporary Containers extension is unmaintained:
https://github.com/stoically/temporary-containers/issues/618
https://addons.mozilla.org/en-US/firefox/addon/containerise/
Default Container: On
Container Name: tmp_{domain}
Lifetime: Until last tab is closed
Rule Addition: *.{domain}.{tld}
Probably Firefox sync, but most likely the extension. I’ll use it again once it works.
Container Number: Reuse available numbers
Delete no longer needed Temporary Containers: After the last tab in it closes
Are there any critical issues with this plugin?