Connecting my iPhone SE to my 2013 iMac
My old (2013) iMac running MacOS 10.15.7 can no longer connect with my 2nd Gen iPhone SE running the current iOS. When I connect with a Lightning cable, Photos keeps re-launching, quitting, and re-launching, and the iPhone will sometimes show up in Finder windows' left-hand column, but if I click on the Phone there then, I get the start of a normal iPhone Finder-window (with back-up, etc), but the main panel just says "Couldn't communicate with a helper application."
And I get intermittent requests to "Please unlock the iPhone," with no change when I do with either fingerprint or access code.
If I reboot either machine with the other running, it makes no difference.
The box in Photos that says "Automatically launch Photos" is unclicked.
Sync automatically is unclicked, as is every other choice I could find...
I vaguely recall automatic downloads of some app in the past, but not clearly.
I want to backup my phone to my Mac, and that's mostly it, although I do store photos on my Mac.
The phone is set to, and does seem to, backup to iCloud, but I can't be sure.
What to do? Is there some way to configure this, or is there some way to download that app manually?
Or is this all just because the Mac and its OS are old and poorly (or un-) supported?
Please advise...
Thanks
iMac 27″