Run `firefox -P` to get a functional GUI. Create some profiles and named them. Create links that run `firefox -P Work`, `firefox -P Personal`, `firefox -P Furries`, whatever. If you have other firefox instances opened, add `--no-remote` to the command line. They are completely separate instances of Firefox, they share only the executable.
You should be able to flip "security.webauth.u2f" depending on your release channel. If not available yet, I think it will be soon in any case.
It's available, and it works for some sites (Github), but not Duo or Google or most sites.
The reason behind this isn't Firefox's fault, Google has a js u2f library that they've written that relies on implementation specific details. It's not easy for Firefox to switch over to that particular unspecced behavior, nor should it, really, so you need to wait for Google to fix it and consumers to pull it in.
Usually the effect of this is that yubikey login doesn't work on some sites, however a couple weeks ago it went to the level that GMail login didn't work at all; it would log you in and show the progress bar and get stuck there (without even throwing up a JS error)
Some/many sites are sniffing the user agent.
And as far as I have googled, there may be a bug in Mozilla's implementation (or maybe a different interpretation of the standard) that they are currently fixing.
Google has a JS u2f library that relies on an implementation specific detail of Chrome's U2F impl. Lots of folks use this library.
In the end they are different from containers in the general purpose (they are geared towards having a multi user experience more than firefox's multi identity/privacy) but chrome's take is much less frustrating to manage in my experience because you can't open the wrong type of tab involuntarly.
That said I switched to firefox and this (and lack of U2F 2nd factor auth) is the only pain point so far