Mac OS X 10.11.6 El Capitan and iTunes 12.8.2.3 and iPhone 12 Pro

I have a very old MacBook Pro and a relatively old iPhone.

I want to get the music currently stored in iTunes onto my iPhone.

Is there any way? Not all of the songs I have are available to re-purchase or stream, so that is not an option even if I didn’t object to paying again.

I have found multiple threads where this was an issue when iOS 17 was released, and workarounds were found – has anyone found a workaround for iOS 18?

I cannot update my laptop further. It is as up to date as it possibly can be.

Late 2008 MacBook Pro

Mac OS X 10.11.6 El Capitan

iTunes 12.8.2.3

iPhone 12 Pro iOS 18.3