The most fascinating feature is the support for post-quantum cryptography (PQC) algorithms !!!

This release adds the following new features:

• Support for server side QUIC (RFC 9000)
• Support for 3rd party QUIC stacks including 0-RTT support
• Support for PQC algorithms (ML-KEM, ML-DSA and SLH-DSA)
• A new configuration option no-tls-deprecated-ec to disable support for
  TLS groups deprecated in RFC8422
• A new configuration option enable-fips-jitter to make the FIPS provider
  to use the JITTER seed source
• Support for central key generation in CMP
• Support added for opaque symmetric key objects (EVP_SKEY)
• Support for multiple TLS keyshares and improved TLS key establishment group
  configurability
• API support for pipelining in provided cipher algorithms

https://github.com/openssl/openssl/releases/tag/openssl-3.5.0