Lately I was trying to migrate some scripts on my desktop to my Android phone, which also runs Firefox. I heard that a lot of extensions that work for the desktop version also work automatically for Android.
Unfortunately, the official Greasemonkey add-on does not work. The same for any *monkey extensions on the Mozilla page.
But I found a way and want to share it with you. There is an add-on called Unified Script Injector that can execute some user scripts (except for GM_* functions, special Greasemonkey functions, which still seem buggy). You can find some userscripts on https://greasyfork.org/.
After installing the addon, you can find the option “USI options” in the settings menu (for me, this is above “Quit” in the menu). The add-on’s page is loaded and provides you with a menu in the left top corner. I could only make the “create new Userscript” menu work, where you can simply paste the wanted script into the field and press Save.
After this, the script should execute correctly on the declared pages. It is not as comfortable as the desktop version of Greasemonkey, but at least it works!