I was wondering the same and so far the only way to do it I've found is via adb with the device connected to your development computer. You can just do this (change com.example.app to the identifier of your app):
I ended up getting this app: https://headjack.io/tutorial/sideload-install-app-apk-oculus-go-quest/ It's worked great. Some apps I've made have crashed badly and won't even show up in Unknown Sources. This app still finds the bad apk and allows me to remove it from my Quest -- something SideQuest failed to do.
If you're in the Quest Link menu (in headset): The same way you uninstall all apps, pointer over it, select the three dots "..." and then select "Remove from Library". If you don't see the app listed in the Quest Link library, disable it and do the following:
From the standard Quest Home (in headset), select your Library (9 squares icon on the toolbar) then select Unknown Sources on the top-right dropdown menu (last on the list), and then select the three vertical dots (... but up/down) and select uninstall.