I don’t know what can prevent you from that 🤔 Maybe totally disabling JS?

Ublock Origin is enough as blocker (It’s so complete in terms of filters. also it’s recommended by Mozilla, and it’s very light). Also Decentraleyes for some third-party contents. Other blockers do the same (they usually use the same blocking lists, too). I only have these two, along with setting Firefox tracking protection to Strict. I guess it’s enough. (Though, you can see UBO wiki to have more advanced blockings.)

I’ve also switched from Debian-based disrtos (Ubuntu) to Arch about two year ago. I installed EndeavourOS and to be honest, it’s simpler in some parts and I understand it better. But in using Arch, you should have a look at wiki too for things you do, since you should do some little things by your own (In my case, it was enabling Bluetooth, Fstrim, Hardware Acceleration, …).

Here’s a good place to start: https://wiki.archlinux.org/title/General_recommendations

Also AUR is a really great way to install any package that it’s not in repos. It actually turn anything into a Pacman package.