After switching browsers, I never actually reinstalled Greasemonkey as uBlock Origin has the capability to inject custom JavaScript.

Check "I am an advanced user", then in "Advanced settings" set the parameter to something like:

    userResourcesLocation file://localhost/home/user/stuff/scriptlets.js

And in the scriptlets.js file, text between the line "/// ScriptName.js" and an empty line is considered a separate scriptlet, which you can add to an URL in "My filters" like:

    news.ycombinator.com##+js(ScriptName.js)

The annoying bit is that scriptlets are cached, and to update them, you have to edit the "userResourcesLocation" setting, for that reason I made "scriptlets1.js" a symlink to the original file and switch back and forth whenever I edit it.