Using old Time Machine external drive with a new computer

Kluunsi wrote:

I know that files on a disk with Time Machine backups cannot be accessed by another Mac using Time Machine. I do not need to access the old files.

My question is, will the old files continue to take up space on the external drive after I start using it for Time Machine backups with a new Mac?

If you want to preserve those old backups start a new backup device.

ref: If your new Mac inherits your backup history - Apple Support

otherwise if you want to recover all the drive space—

Erase and reformat a storage device in Disk Utility on Mac

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology.