It can be made to work in largely the same way. You just need to install the extra plugin (and associated extra component). I have a similar number of profiles as you and I haven’t had to change how I work.
The article comments reference Multi-Account Containers, but I’m not sure I could make them work. I need different bookmarks for each profile, and I like the separation of a new window.
No idea if it’s related, but I see similar behaviour (the not loading, rather than the error message) whenever Firefox requires a restart for an update. It doesn’t make it clear this is what is happening, it just stops loading web pages in existing tabs. Only if I open a new tab does it show the “Restart to keep using” message.
I’ve spent far too much time diagnosing network issues without realising I just needed a restart :)