Disabling jN solves it although I lose all the plugins that depend on it.

Then put in the request with the jN developer, as I already linked. In the mean time, your choices are to live without jN and the plugins that depend on it, or to revert back to an older Notepad++ that came before the API change (v8.2.1 should work) so that you can still use jN and those others that depend on it.

This is making me suspect the culprit is most likely the jN Npp plugin, but I am not sure.

Very likely, yes. That plugin has not been updated since 2020, so it has not had the API fixes necessary to make it 100% compatible with Notepad++ v8.4.2.

Is there any way to find out why Notepad++ is crashing?

You can easily find out if jN is the culprit: Temporarily remove jN Npp (exit Notepad++; rename the folder C:\Program Files\Notepad++\plugins\jN\ to C:\Program Files\Notepad++\plugins\jN.disabled\; run Notepad++; see if it crashes. To re-enable the plugin, rename the folder back). If it still crashes after disabling the plugin, the plugin isn’t the culprit; if the crashes go away, the plugin is the culprit.

I need to use that plugin, so if it indeed is the plugin that is causing the crash, I would like to have a workaround for it. Will an older version of Notepad++ work better with that plugin?

Since the API changed in v8.3 (due to the support for filesize >= 2GB), you should be able to use v8.2.1, which is the last version before the 2GB feature update. I also recommend creating an issue for the jN Npp developer, asking them to make their plugin compatible with the updated API.