Firefox/librewolf has currently two ways to create profiles (per profile or objective, it’s on you). I prefer the old way (small classic GUI to select a profile) because I can set it to open it on start prior opening a default profile. I like it since i can decide which profile should open a link I found on VSCode or a script or any other source or even to reject opening a link in case I just misclicked.

How to do it?

Base command (Flatpak)

flatpak run --branch=stable --arch=x86_64 --command=librewolf --file-forwarding io.gitlab.librewolf-community @@u %u @@

With ProfileManager (profile selector on launch)

run --branch=stable --arch=x86_64 --command=librewolf --file-forwarding io.gitlab.librewolf-community --ProfileManager @@u %u @@

With specific profile (no selector)

run --branch=stable --arch=x86_64 --command=librewolf --file-forwarding io.gitlab.librewolf-community -P ProfileName