How to fix the sys.host_summary table in MariaDB 10.3.13 using mysqldump while doing a backup gives the following error:

mysqldump: Got error: 1356: "View 'sys.host_summary' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them" when using LOCK TABLES


What can I do to fix that?
The sys schema is not bundled with 10.3, but seems to be planned for 10.5. If you don't use/need it, you can safely remove it: DROP DATABASE sys;. If you do need it, you need to try resolving the issue outlined in the error message. For a start you can do SHOW CREATE VIEW sys.host_summary; to see which tables, views and functions it's referencing, as well as the definer/invoker.