I think that things like HTML validation can still be useful for two reasons:
- When you are creating layouts it’s easy to create non-compliant or a least somewhat questionable HTML. Validation makes sure you catch that.
- I’ve managed to have situations where content, in combination with the layout, has created invalid HTML, but it takes particular content to trigger the issue.
I don’t know if you have seen the audit for Hugo that Joe Mooring has created, or my scripting of same:
For the majority of the tests I’d suggest that they are off-top as not being Hugo-specific or being more about what providers you use (e.g. GitHub actions, whatever GitLab uses, Netlify stuff, etc).