Why can't I convert to mp3 anymore so I can burn to a disc?

My own music library was quite extensive and I also have an Apple Music subscription.

We have very poor internet and I want to have discs for some of my playlists.

In the past I was able to convert files in my own library to mp3 and burn to disc. I understand I cannot burn any to disc that I've just downloaded from Apple Music without purchasing it.

My problem today is that when I try to burn the playlist to disc - it rejects about half of them, which is far more than what it should be as most were in my own library to start with.

When I go to File/Convert - I only have 2 options, 1 to create ID3 tags and 2 to convert to AAC files. There used to be an option here previously to convert to mp3 (from memory).

I don't think I want ID tags, but am not really sure about that. AAC files are too big and would require many more CD's to burn the playlist.

When I look at the 'kind' of files in my playlist they are a mix of:

• AAC audio file
• Apple Music AAC audio file
• Matched AAC audio file
• MPEG audio file
• Purchased AAC audio file

Can someone tell me which are being allowed to burn and which not?

Many of these songs were in my library before I joined Apple Music - I should be able to burn them to disc. How have their file types changed?

How can I convert them once again to mp3 which no longer seems to appear anywhere?

Is there any way to generate a list of the ones that will be burnt? The CD burns but the playlist data seems to stay the same, even though it has not burnt all the songs?

Thanks