Custom user styles might work on Chrome, but on Firefox mobile, it's an atrocious experience. You need to install the nightly version, set some hidden developer

Custom user styles might work on Chrome, but on Firefox mobile, it's an atrocious experience. You need to install the nightly version, set some hidden developer flags, create a addon collection with your user account on addons.mozilla.org and type the collection ID in the settings of your mobile browser. In other words, you can't really do it.