I have the same problem but from going from v11 to v13. The console is giving me mixed block error but no amalgamation of different http/https and address settings work or change anything, it either breaks the whole website or th esame seadoc. Currently I have everything set back to what the caddy docker automatically has and everything is going through my Nginx Proxy Manager and cloudflare.
https:// seafile.domain. com/sdoc-server is just 404 and opening any sdoc file gives this error Blocked loading mixed active content “http:// seafile.domain. com/sdoc-server/api/v1/docs/filenumbers\~/”