I tried to remove DRM with Apple Music Free Trial and it didn't work.

If you download past purchases from the Apple Music Library rather than the iTunes Store Library they will have DRM added even if they didn't have it before and therefore will cease to be playable if you stop the subscription.

If you download past purchases from the iTunes Store Library this will not apply, but if they are older purchases which have DRM they will still have DRM. If you subscribe to iTunes Match these downloads will not have DRM, and this is independent of whether or not you have Apple Music (though in the latter case it's still a case of downloading them from the iTunes Store Library rather than the Apple Music Library).

If you decide that you don't want Apple Music (with its ability to stream or download from a large library) and would rather have iTunes Match by itself, you should note that a) you should cancel Apple Music more than 24 hours before the expiry of the free trial to avoid being charged, and b) when you cancel the free trial, even if it's some way ahead of expiry, you will immediately lose access to Apple Music.

See if this helps: https://support.apple.com/HT205919

AFAIK there is no bulk way of doing this. But Apple Music won't remove DRM. This is the info on iTunes Match:

iTUNES MATCH

This makes all items in your iTunes collection available online for access to your other devices. Songs you have purchased will be available, as with 'Tunes in the Cloud'; songs you have for example ripped from CDs you have bought will be matched by the version in the Store if this is available; if it isn't available your copy will be uploaded for access by other devices.

There is a limit of 100,000 songs - this applies only to items not available in the Store (as purchased items are already available online). There is a charge of $24.99/£21.99 per year. The storage for these items does not count towards your iCloud storage space (indeed, though marketed as being part of iCloud it's actually nothing to do with it). Items in iTunes Match are not affected by DRM (Digital Rights Management which restricts where you can play them).

Once downloaded you can still play them if you terminate the subscription (though in that event you can't make further uploads or downloads).

See also About iTunes Plus - Apple Support.

tt2