so I'm a total beginner when it comes to SSL/TLS certificates. I have generated a few of them using OpenSSL for some local servers in my LAN. I have already built and expo react native app working 100%, but when I build the APK, and install it specifically on android devices, Im getting this error:

    java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.
 (NOBRIDGE) LOG  Connection closed 1006 java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.

The root CA certificate was generated using openssl, and the reverse proxy server is using a signed-server certificate signed by this root CA I created.

My question is:

Since android is not allowing "User" certificates and only allows "System" certificates, is it possible to obtain a certificate from LetsEncrypt for this reverse proxy local server? That way android can trust the reverse proxy certificate and the expo app could connect fine to the backend server.

Basically the servers and clients will all be running in my LAN only, not open to the internet.

This is just for a small learning project in my LAN.