Wait.. does this make the profile switching UX nearly identical to chrome? I abandoned a switch attempt because I found containers inadequate and profile switching too cumbersome.

Correct.

I don't trust extensions, so yes.

That is not an extension maintained by Mozilla. Why do you think it’s needed for profiles? Profiles are built into Firefox and don’t need an extension to be used.

it immensely helps in creating and switching profiles. it is like how firefox support tab containers, but multi-container extension improves UX

The in-browser support/UX - the ever present menu options and keyboard shortcuts - are what make Profiles so much better to use in Chrome than in Firefox. The extension attempts to bridge that gap.

Having to use about:profiles or an external application shortcut is a much worse experience overall.

What I said was that the profiles extension requires an install, not that profiles requires an extension.

It just significantly improves quality of life when working with profiles, not that it is required.

It's also unfortunately kind of broken (or it was last time I used it)

about:profiles is not pretty but works without installing 3rd party extensions.