"This song is not currently available in your country or region" error for uploaded content

Preface: I am not an Apple Music subscriber. I pay for iTunes Match (yes, still, in 2022). I manage my local library of my own MP3 files in the Music app on a modern Mac. I use iTunes Match as a way of having my music automatically, wirelessly appear on my iPhone.

For the past couple years I have been increasingly encountering the error, "This song is not currently available in your country or region" for MP3s that I maintain and upload. The song title is grayed out.

My suspicion is that the syncing service that was historically used with iTunes Match has now merged with Apple Music and this has something to do with the fact that these tracks are now getting ID'ed and associated with releases internationally that might not be available in USA where I am located. I notice it happening often with European and Asian artists. This was never a problem in the years before Apple Music became a product and everything was just iTunes Match.

I don't care whether something is available on a streaming platform in my region or not - that's why I still bother with a local library in the first place. I want my library to be private and always accessible. Is iTunes Match no longer appropriate for me, if that's the case? If so - what is the best way to continue to use the Music app on my Mac, and have the same songs available to me on my iPhone? Wired syncing?