I'm try to follow the instructions provided by Don Marti at https://blog.zgp.org/scale-20. This involves adding an extension to Firefox but it doesn't work for me. Evidently it does work for Don on some other version of Linux.
I'm running Firefox 110 on Fedora 37 with KDE. I have successfully installed the desired extension, "Multi-Account Containers", but do not see the container icon. I can reach the container management page via the Addons link and have added a YouTube container. And the addon is enabled. But I can't find any way to say, ���������always open this site in container���������.
In case it matters, I see that FF's addon page reports that this addon requires container tabs and marks the addon as disabled. If I enable them and then enable the addon, when I return to the addon page, it shows the container tabs option checked but dimmed, the only option for the addon itself is "Disable Extension".
I have also reported this to Mozilla (https://bugzilla.mozilla.org/show_bug.cgi?id=1823561) but, since this behavior seems to be unique to my situation, I'm also reporting it here.