SLCW on Nostr: That's why. There is a Chrome version of the extension, but for whatever reason, ...

That's why. There is a Chrome version of the extension, but for whatever reason, Chrome and Chromium variants on Android do not support extensions. Only the desktop version does. If you want to use extensions on Android, you have to install Firefox, or a Firefox-based browser as they fully support extensions. I recommend Mull, Fennec, or Ice Raven. They're optimized, privacy enhanced, and security-hardened versions of Firefox that are significantly better than basic Firefox. Once you do, installing Nos2x is as easy as going into the Extensions Manager, accessible from the main menu, installing the Nos2x extension, and then setting it up with your nostr nsec.