Can I revert to previous iOS? - iPhone broken again w/ iOS 13.1.3 and iTunes/ OS 10.10.5

Because I MUST use Yosemite 10.10.5 to not break my 'breadwinner' software on this computer, I am unable to update the computer OS. If I could, I would.

I always update the iOS for my iPhone SE but those updates will variously and unexpectedly break compatibility between the phone and my Yosemite/ iTunes computer.

So, iPhone/ iTunes compatibility is broken AGAIN with iOS 13.1.3 + iTunes (12.8.1.3)

The previous iOS release worked, several before that did not.

Why is it Apple can use my phone to verify my identity for posting here for instance (under Safari/Yosemite) but iOS updates break the phone's ability to mount and communicate with my computer/iTunes??

The phone still shows up within iPhoto, but not iTunes.

I'd like to find a path to revert to the previous iOS....Any helper elves out there...?