Can you use 'Developer tools' plugin to catch the error?

Switch on 'Enable error log' in the plugin's settings and reproduce your issue.

Now check out /admin/develop_tools/error_log

Because the log you provided doesn't clarify the details.

We'll have a look https://github.com/Elgg/Elgg/issues/14842

Will be fixed in the next Elgg release. https://github.com/Elgg/Elgg/pull/14849

It indeed seems to come from "Site settings - 'Default number of items per page'."

For a quick fix, I changed it to 100, as I don't have that many pages in any of the sections yet (e.g. blog, pages, events). But it's not the best solution.

I'm not sure now if this is working as intended or not. If it's a bug, how/where would I report it?

how/where would I report it?

https://github.com/Elgg/Elgg/issues

You can temporarily fix this adding 'limit' => false to "PagesNav.php"

'batch' => true,
'limit' => false,
'sort_by' => [
   'property_type' => 'metadata',
   'property' => 'title',
  'direction' => 'ASC',
],

Will be fixed in the next Elgg release https://github.com/Elgg/Elgg/pull/14834

I can't reproduce it, all works as expected.

Deactivate all 3rd-party plugins and try again.