mariabackup documentation states :

A MariaDB Server version can often be backed up with most other Mariabackup releases in the same release series. For example, MariaDB 10.2.21 and MariaDB 10.2.22 are both in the MariaDB 10.2 release series, so MariaDB Server from MariaDB 10.2.21 could be backed up by Mariabackup from MariaDB 10.2.22, or vice versa.

However, occasionally, a MariaDB Server or Mariabackup release will include bug fixes that will break compatibility with previous releases. For example, the fix for MDEV-13564 changed the InnoDB redo log format in MariaDB 10.2.19 which broke compatibility with previous releases. To be safest, a MariaDB Server release should generally be backed up with the Mariabackup release that has the same version number.

That’s a good start, but does not answer all questions a user can ask about compatibility issues/non-issues when using mariabackup, and I can’t find any other place where this is discussed.

IMO, the documentation should answer those questions :

• If I create a backup (mariabackup --backup) with mariabackup 10.x.y, what versions of mariabackup are capable of restoring it (mariabackup --prepare) ? Any more recent mariabackup version will do ? Or does the serie ( x ) has to match ? Does the minor version ( y ) has to match ?
• I create a full backup with mariabackup 10.x.y. What are the constraints on the version of mariabackup if I want to create an incremental backup from it ? Any more recent version will do ? Or does the serie has to match ? Or does the minor version has to match ?
• I have a full backup made on 10.x.y, and an incremental backup made on 10.a.b based on it. Do I have to perform any special step to restore the incremental part, such as running mariadb 10.a.b first on the full backup to upgrade the data ?