500 error when accessing /jsonapi/

Drupal 9 is end-of-life. Also, the exception details are not shown.

Thanks both.

I'm aware of 9.5 EOL and am thankful for the reminder here. On this particular project the d10 upgrade hasn't happened yet, and there was a need to resolve this issue to unblock a front end dev. I'd hesitated to put this up here, but figured it was worth seeing if it had occurred for others.

That said, after rolling back and stepping through each of the updates, we've narrowed it down to the JSON:API Book → module. When we back this out the problem goes away, and it seems to be interfering with the ability to redirect to /en/jsonapi

We are investigating to see if we can recommend a fix there, and will follow up with an issue on that module page to document it.

I'm unsure what best practice is for this issue.

We don't think that it is a JSON:API issue itself. Shall we close this and then I can comment here with the link to the JSON:API book issue when we create it?

Thanks