Update — I have had good results with 5.7.1!
Tested EL9 + kamailio-tls (packaged module, i.e., not locally compiled): * kamailio-5.7.1-0.el9.centos.x86_64 * openssl-3.0.7-16.el9_2.x86_64 * concurrent 500 UAs, 500 connections/s
Same load test as with OpenSSL 1.1.1, and tls_wolfssl.
I will continue to test Debian bookworm/Ubuntu 22.04 LTS then I think this ticket can be closed.