I have two problems that are (I think) connected
1. Installed nextcloud, letsencrypt, duckdns, airsonic etc. from linuxserver.io. Set up nginx reverse proxy. From my desktop, while I am on local LAN, I can perfectly browse for example: https://nextcloud.mydomain.duckdns.org/. Also, I can freely open it from my work desktop via internet. On my Android phone, while on mobile data, every domain open w/o problems, but I can not open any domain if I am at local LAN (the same LAN server is) with wi-fi connected. Any help, please?
2. Install Openvpn-as. Connect to server from my phone (mobile data only). Can browse https://nextcloud.mydomain.duckdns.org/, but can't browse 192.168.1.1 (or any site from my server which is not exposed to internet, like OMV web portal or Heimdall).
Good people on linuxserver discord suggest that I need split DNS. The problem is that I have no idea how to do that. And - my router (from internet provider) don't allow me to change DNS server. I am stuck with my provider DNSs. Any thouts, please?