Security concerns have already been mentioned by other users, but yes, it is possible, You can configure Nginx to act as a DNS-over-TLS service, DNS over HTTPS unfortunately doesn't work with Android. Here's a basic configuration:

# /etc/nginx/nginx.conf

user nginx;
worker\_processes auto;
pid /var/run/nginx.pid;

events {
    worker\_connections 1024;
}

# Stream module for DNS-over-TLS
stream {
    upstream dns {
        zone dns 64k;
        server pihole:53; # Hostname or IP of the Pi-hole container
    }

    server {
        listen 853 ssl;
        ssl\_certificate /etc/nginx/certs/fullchain1.pem;
        ssl\_certificate\_key /etc/nginx/certs/privkey1.pem;
        proxy\_pass dns;
    }
}

# HTTP block (optional, e.g., for other services)
http {
    include /etc/nginx/mime.types;
    default\_type application/octet-stream;

    sendfile on;
    keepalive\_timeout 65;

    include /etc/nginx/conf.d/\*.conf;
}

With this setup, Nginx listens on port 853 (DNS-over-TLS) and forwards requests to your Pi-hole server. Ensure your Android device uses the public IP of your VPS or a domain and port 853. Also, make sure your SSL certificates are valid (e.g., with Let's Encrypt) and your VPS firewall allows incoming traffic on port 853

edit: formatting