You can use about:profiles or the profile manager (https://support.mozilla.org/en-US/kb/profile-manager-create-...) to handle that. The UX isn't as polished, but for just a handful of uses (work, personal, etc.) it's easy enough to make shortcuts which call `firefox --new-instance --profile <profilename>`.

You can use multiple profiles with Firefox, the UX for doing so just isn't as fleshed out as Chromium.

Create a new profile by going to about:profiles, and thereafter when you start Firefox it should present you with an option to pick which profile to use.