Looks like UICN is doing something wrong on their side (missing cert files?). I've tried sslv2, sslv3, tls1, tls1.1 tls1.2, and tls1.3, I basically get the same error.

kindone@laptop:~$ openssl s_client -connect irc.uicn.net:9999
139745690408064:error:1408F10B:SSL routines:ssl3_get_record:wrong version number:../ssl/record/ssl3_record.c:332:
no peer certificate available
No client certificate CA names sent
SSL handshake has read 5 bytes and written 304 bytes
Verification: OK
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)

irc.swiftirc.net #msl (mIRC Scripting Language)