As mentioned in https://github.com/MariaDB/server/pull/2054, when doing a limited backup maybe BACKUP LOCK tbl is sufficient.

monty is there a reason BACKUP LOCK tbls requires RELOAD privs? Would a table level privilege be sufficient? A SELECT statement in a transaction is sufficient to hold a metadata lock so couldn't that apply to {{BACKUP LOCK}}s too?

About RELOAD. The documentation is:
"Execute FLUSH statements or equivalent mariadb-admin/mysqladmin commands."

In effect having RELOAD privilege is not something that should cause any issues to give to anyone.
It is more that anyone having RELOAD could potentially do a lot of not needed FLUSH commands, which could any people on busy server.
Same thing with BACKUP STAGE as one can stop DDL's if one is not using it carefully.

When it comes to BACKUP LOCK, having access to the table should probably be enough.
I will check with Sergei.

The conclusion would be to allow one to do a BACKUP LOCK if one has either the global RELOAD privilege or the LOCK privilege on the table.
This makes BACKUP LOCK similar to LOCK TABLE, but still backward compatible

mydumper patch on his way: https://github.com/mydumper/mydumper/issues/8 with some documented case

Agree that making an additional privilege in addition to RELOAD is the easiest compatible way.

LOCK_TABLES_ACL appears to be a database level privilege, which in addition to SELECT on the table give access to LOCK TABLE, so that pattern can be copied.

Which major version should this change target?