I came to say this. And not flippantly. Each one of these takes a dive into the documentation to resolve. Sometimes they are related and you can solve some issues with one change, but each one is a challenge to be solved.
OP, focus on Security first, Errors second, and warnings third. Often the warnings are not a huge deal to having an operational nextcloud, but might impact performance or excessive logging for example.
I came to say this. And not flippantly. Each one of these takes a dive into the documentation to resolve. Sometimes they are related and you can solve some issues with one change, but each one is a challenge to be solved.
OP, focus on Security first, Errors second, and warnings third. Often the warnings are not a huge deal to having an operational nextcloud, but might impact performance or excessive logging for example.