Documents folder in Sharepoint doesn't open behind App proxy

Question

Trying to publish an onprem sharepoint 2019 via app proxy. The login works very well and I can see the sharepoint home. But when I try to access any library like Documents or Pages it just hangs, like it is waiting for something. The dots moving across the top of the screen. No settings cogwheel or account details.

Eventlog in App proxy logs nothing.

If I access the sharepoint directly, all the libraries work. The current setup is an app proxy and a test sharepoint on server 2019, domain joined and in the same subnet.