I already found answers for older versions here and here but as far as I can tell none of it directly translates into drupal 9.
The matter in practice: I don't have a huge experience but I was very surprised when in the not so complicated setup I'm building I could see the page of a taxonomy term but none of the items in it under the introductory text when viewing the page as anonymous user. Viewing one of the nodes by direct url results in "Access Denied".
Not much at play, all items are published, permissions look good and I already rebuilt permissions and caches so I'm looking for something like raw printing yay/nay permissions being applied and so on. Even looking directly in the database would be ok if applicable.