looking for a CD player compatible with a Mac Mini M4

Most modern USB-powered external drives are plug-and-play with macOS, so you don’t need extra drivers. Apple used to sell the Apple USB SuperDrive (which you can still find on the Internet), which still works perfectly fine on modern Macs using USB-A. Since your Mac Mini M4 only has USB-C/Thunderbolt 4 ports, you can connect the SuperDrive with Apple’s USB-C to USB Adapter.

If you want something non-Apple’, there are many third-party options (like LG, Pioneer, or ASUS external CD/DVD drives) that should work fine.

You can get one for less than $25 on Amazon, for instance. I bought maybe 3 different ones. I was recovering pictures off old CD and DVD backups that I had made over the years, and there were some files that one drive would read but another wouldn't.

However, for professionally produced CDs DVDs, it didn't seem to matter at all how cheap the drive was.

You're very welcome!