Harvey I highly doubt the new update will do much for you as it simply moves FF from using bundled libicu back to system libicu again and we've been using bundled since 31st May so clearly not related.
Thank you for the info.
Harvey If it were me I would try deleting ~/.mozilla/ forcing it to start completely fresh. This will result in bookmarks, saved passwords, history, extensions, settings, active sessions etc being lost for FF so back it up first if that is important to you. See how it goes.
I'm going on holidays, so I won't have access to my desktop computer for a few weeks. When I'm back, I will update it, and if I keep having this problem, I'll try this.
I'll probably take my laptop with me (also Solus), so I'll see if I have the same problem with Firefox on my laptop. So far, I had this problem only on my desktop machine.
Today, I have been browsing (Firefox, my desktop machine) on Reddit to check if anything bad happens, but everything was OK.
Staudey Maybe some config issue, or related to one of your installed add-ons?
I use Ublock Origin and Plasma Integration, but I have always used them.
qsl I had the whole system go unresponsive a couple of times recently, but hard to say if it was specifically Firefox (it was open).
I had this problem with Firefox, but not with Brave, for example.
qsl what is the equivalent to task manager?
It depends on your desktop:
Budgie and Gnome: Gnome System Monitor (as brent said)
MATE: MATE System Monitor
KDE Plasma: Plasma System Monitor, and Ksysguard
Thank you everybody who tried to help me. I will update this thread.