PostgreSQL is v12 for Ubuntu. I would recommend trying to adding the official apt repo from the before mentioned link and upgrading to a supported version of server, client and driver.
I have postgresql 9.6 running on Ubuntu server 16. After upgrading it to 18, it was running fine. And I upgraded to 20, the service is not coming up. Below is the error seen in logs. I have debezium configured and even tried compiling it again on 20. But it did not help.
FATAL: could not load library "/usr/lib/postgresql/9.6/lib/decoderbufs.so": /usr/lib/x86_64-linux-gnu/libSFCGAL.so.1: undefined symbol: _ZlsRSoPK12__mpz_struct