I'm almost sorry to ask this, but does anyone have experience with Firefox on Linux taking a long time to open? I'm running Pop!_OS on a fairly modern machine. All other programs open pretty quickly, but Firefox seems to drag its feet on startup. Once it's open it's great, no problems with speed.
I have tried disabling extensions (ublock origin, sponsorblock, decentraleyes, i still don't care about cookies) and I have tried setting my default profile as one without any custom user.js (I have a profile with Arkenfox and one with Betterfox's user.js). Nothing I have done so far has seemed to make any difference, but Help->Troubleshoot Mode allows Firefox to open quickly, so there must be something that I can disable that is causing the issue... Any ideas? Thanks.
Edit: Seems like swapping to the flatpak version made things much faster. The Pop!_OS .deb version must be snap like you all said :) Thanks everyone!
If OP is on Ubuntu, it's a snap.
I personally don't have any issues launching Firefox, which is installed as a regular app and not a snap/flatpak. It's basically instant for me, maybe 2-3s if I have a ton of tabs or something. I haven't tried the flatpak, but I'd be surprised if it adds more than a second or so, because other flatpak apps launch reasonably fast.