Sick of Mac denying access to my own files!

Try setting up another admin user account in System Preferences/Users & Groups to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. If the log won’t post, try posting it in Pastebin and provide a link in a reply. After pasting the report in a PasteBin page, go to the top of the page, and copy the address in the URL bar. Paste that in a new reply.        Pastebin

Etrecheck – System Information

Bottom line? Security is only going to get more restrictive going forward. Every new release of macOS (and other operating systems; Windows is no exception) will come with more stringent security measures due to the increase in bad actors that are trying to "get into your data."

Any workaround, will just need to be re-done at some point in time. That's just the way it is. You can elect not to participate by not buying these products ... but you will eventually not be able to use computers at all. Ah, for the simpler days, when a "handshake" was all that was needed.

I wasn't trying to be argumentative, just stating today's reality. I'm sure you will get plenty of replies with differing opinions ... and potential solutions. Maybe someone, well versed with Android devices, will offer you a solution that worked for them.

The issue, IMHO, is that any solution will just be trying to solve a "moving target." Apple will continue to tighten security measures with each OS update, as will Google with the Android OS. We have seen this with every new version of OS X, and even more so, with macOS. This would all "go away" if the "bad guys" do ... not likely to happen anytime soon.

If you want me to offer solutions which reduces or even eliminates any security measure that Apple has implemented in their OS, I can certainly provide a few ... but they all come with their own risk and I wouldn't recommend doing any of them.

Well if this was normal behaviour for a mac then we would all be stuck. My Mac can take images of of phones

of all kinds and a multitude of other devices, cameras, etc and have never encountered the problems you are having. This leads me to think there may be some sort of app installed on the Mac that is applying some sort of security permissions on files imported. So can you find out if there is any such software installed, and report back.

Are you sure the photos are also getting the correct format at the transfer (they have a different format on the phone).

How do you transfer the photos to the mac, iTunes? iMazing?.