Web interface response is 501

[teras]

When I turn on the web interface (Raspberry Pi 4, OSMC distribution) instead of having the welcome screen, I get this:

Error response

Error code: 501

Message: Not Implemented.

Error code explanation: 501 - Server does not support this operation.

Other interfaces, including its own, works. What could be the problem?

[tuxfamily]

Same issue IF the URL ends with a slash.

I mean, this work:

http://192.168.1.20:50152/api

this doesn't

http://192.168.1.20:50152/api/