Websocket on different port

[metaathron]

Hi. I'm trying to proxy my 3D printer's web application. It uses http on port 80 and websocket on port 9999. I have created proxy https://printer.domain.tld -> http://192.168.27.209:80.
Now I can see, that the page requests wss://printer.domain.tld:9999. I am able to open port 9999 to printer or npm, but the printer uses WS, not WSS. Is there a way to force it to WS or proxy WSS to WS on 9999?