Comment # 3 on bug 1207963 from Michael Hamilton

Thanks for the prompt response.  Unfortunately, I'm still getting TLS errors.

I've experimented using rpm to change between versions:

# rpm -q --changelog
/var/cache/zypp/packages/Tumbleweed_KDE3/x86_64/kdelibs3-3.5.10-242.1.x86_64.rpm
| head
* Wed Feb 08 2023 Yasuhiko Kamata <belphegor@belbel.or.jp>
- Added kdelibs-3.5.10-ossl-3.patch for supporting openssl 3.0
  (SSL_get_peer_certificate() was renamed to
  SSL_get1_peer_certificate, boo#1207963).

# rpm  --upgrade
/var/cache/zypp/packages/Tumbleweed_KDE3/x86_64/kdelibs3-3.5.10-242.1.x86_64.rpm
Verifying packages...
Preparing packages...
kdelibs3-3.5.10-242.1.x86_64
/opt/kde3/bin/kpac_dhcp_helper: no configuration entry in active permission
profiles found. Cannot check this path.
kdelibs3-3.5.10-241.16.x86_64

# rpm -q --changelog kdelibs3 | head
* Wed Feb 08 2023 Yasuhiko Kamata <belphegor@belbel.or.jp>
- Added kdelibs-3.5.10-ossl-3.patch for supporting openssl 3.0
  (SSL_get_peer_certificate() was renamed to
  SSL_get1_peer_certificate, boo#1207963).

# zypper ps -s  # check that all kmail kde3 kdeinit processes and are gone or
reboot

Back to getting TLS errors, so I rebooted to be sure, but that didn't help. 
I've appended a journal message that was logged to the end of the comment.

I reverted to old package:

# rpm --upgrade --force
/var/cache/zypp/packages/Tumbleweed_KDE3/x86_64/kdelibs3-3.5.10-241.16.x86_64.rpm

# zypper ps -s  # check that all kmail kde3 processes and are gone or reboot

I restarted kmail, no TLS errors.  

Now that the linkage issue is resolved, could there be some other settings
changes needed for openssl 3.X - perhaps for backward compatibility?

-------- Journal message follows:
Journal Entry 2023-02-08 17:29:15.137584+13:00

MESSAGE                  : 409FC5BA497F0000:error:0A000102:SSL
routines:ssl_choose_client_version:unsupported
protocol:ssl/statem/statem_lib.c:1952:
PRIORITY                 : 6
SYSLOG_FACILITY          : 3
SYSLOG_IDENTIFIER        : plasmashell
_AUDIT_LOGINUID          : 500
_AUDIT_SESSION           : 4
_BOOT_ID                 : 9109cb9b-0f7e-418d-b434-110bee0dec11
_CAP_EFFECTIVE           : 0
_CMDLINE                 : "kio_pop3 [kdeinit] pop3 /tmp/ksocket-michae"
_COMM                    : kio_pop3
_EXE                     : /opt/kde3/bin/kdeinit
_GID                     : 500
_HOSTNAME                : kosmos1.gentoo.co.nz
_MACHINE_ID              : f46fb36d-a070-7527-1a4e-af8f58081717
_PID                     : 5267
_RUNTIME_SCOPE           : system
_SELINUX_CONTEXT         : unconfined

_STREAM_ID               : 44c5230e15a34ee9a7d72dcd339fd9e4
_SYSTEMD_CGROUP          :
/user.slice/user-500.slice/user@500.service/session.slice/plasma-plasmashell.service
_SYSTEMD_INVOCATION_ID   : 5c457c19b2b045758c806dd626e56c8c
_SYSTEMD_OWNER_UID       : 500
_SYSTEMD_SLICE           : user-500.slice
_SYSTEMD_UNIT            : user@500.service
_SYSTEMD_USER_SLICE      : session.slice
_SYSTEMD_USER_UNIT       : plasma-plasmashell.service
_TRANSPORT               : stdout
_UID                     : 500
__CURSOR                 :
s=aa0a9e554fe34b308777e5fc5d3112c6;i=31b01b;b=9109cb9b0f7e418db434110bee0dec11;m=56aba6ca;t=5f428b4f15630;x=51f3588561bcf708
__MONOTONIC_TIMESTAMP    :
journal.Monotonic(timestamp=datetime.timedelta(seconds=1454,
microseconds=89930), bootid=UUID('9109cb9b-0f7e-418d-b434-110bee0dec11'))
__REALTIME_TIMESTAMP     : 2023-02-08 17:29:15.137584+13:00