Issue Plesk NodeJS Server CORS error

[Patrick Meppe]

Good evening.

I'm having a similar problem to the following: https://support.plesk.com/hc/en-us/...s-origin-resource-sharing-in-Plesk-for-Linux- .
In my case I'm trying to run a NodeJs server. http2 & Nginx are active.
The NodeJS server is directly accessible over the browser, but not as the target of an AJAX request.

I have tried all the suggestions above and more:
Apache & nginx Settings for

I even temporally deactivated HTTP2. No success.
Any other suggestions?