/public was indeed missing from APP_URL, its now /invoiceninja/public
Though that still does not seem to fix the problem entirely, here again the error when trying to open /invoiceninja/public/index.php
Not sure if the error could be in the invoiceninja/config/livewire.php, looking at an older setup of invoice ninja I had ‘asset_url’ => env(…), in the current file it was just => null. I changed it as below:
And now at least the Livewire Error is gone, though I still get a 500er when going to /public/index.php
Thanks again for the quick & targeted help.