How did you download the app? IPhone user here ...I know how to side load on Android but not on iPhone.
He likely has a Droid...you can still download the app on that type of phone just not from Google play
That is why Apple will get it in trouble I think
....you can’t even download an app on an I-phone unless it is from the apple store
like Microsoft with the IE issue back in the day
See my #19 how to get the app on iOS.
Just use “Gab.com”? Pretty sure you can use your current browser (Brave.com for me now)to get there.