Can I safely remove ~/Music/iTunes/iTunes Media/Mobile Applications without destroying my back up?

Sorry, I don't follow you, Neil. It seems Apple has removed the ability to install an iOS app from itunes in iTunes 12.7. I am assuming all that gets backed up in itunes is your app files and settings?

Looking at I back up my ~/Music/iTunes/iTunes Media/Mobile Applications folder nothing has been updated since about the time iTunes 12.7 came out on 9/12 even though I back up my iOS device at least weekly.

I am assuming that going forward, one can't backup apps from iOS to the Mac for reinstallation?

Let me clarify a bit to be very precise.

No apps seem to be being backed up to ~/Music/iTunes/iTunes Media/Mobile Applications any more. So if I don't care about using this workaround for apps that are no longer in the store anymore, is there any reason to keep this directory on my Mac? at 31GB it is a sizable chunk of disk.

Understood. But I've confirmed that that folder hasn't been updated since iTunes 12.7 was released on 9/12. So no new apps will be put in there going forward. Apple Support confirmed that as well.

While it is true the whole idea of local backup to the mac was to circumvent apps removed from the store, I never actually used that feature and, since itunes won't have any apps put in that folder going forward seems like a big waste of disk space to me.