Hi,
There are/will be no new updates to Mojave. If you're running 10.14.6 and installed the last Security Update 2021-005 released July 21, 2021, Mojave is as up-to-date as it will ever be. If you didn't install those, I don't know if Software Update will still work, but you can try. Go to System Preferences > Software Update (do NOT click on Upgrade Now for the OS upgrade) > Advanced > Check for updates > OK and see if any show up. If so, you can download/install those.
As for browsers, Safari also does not receive security updates, so it would be a good idea to download/switch to Firefox, Google Chrome, or Brave to name a few.