Hello,
I faced a problem in Turris OS 7.1.0 when over secure http the main page https://your-router-ip-here/ is rendered with the following error: Expected JSON, got null
(Note: plain http doesn’t have this problem but I prefer using https)
Restarting lighttpd and/or router didn’t help.
As a workaround I tried the url https://your-router-ip-here/login?/reforis/ and it worked fine.