upgraded to centos stream, strongswan-services won't start about strongswan HOT 2 CLOSED

Check what package /usr/sbin/ipsec belongs to. If it belongs to libreswan, you forgot the rename the ipsec binary of strongSwan to strongswan (because that's one of the things that are done in RPM packaging on RedHat platforms (RHEL, Fedora, CentOS, ...).
Besides that, they moved the configs all from /etc into /etc/stronswan (e.g. /etc/strongswan/strongswan.d).

from strongswan.

Please report bugs in EPEL packages to Red Hat bugzilla, component strongswan. If that packages are broken, we would like to know it.

Are you sure you did not override ExecStart ofr the service? It uses different command on Fedora, I do not think it should be different on EPEL8.

# systemctl cat strongswan-starter
# /usr/lib/systemd/system/strongswan-starter.service
[Unit]
Description=strongSwan IPsec IKEv1/IKEv2 daemon using ipsec.conf
After=syslog.target network-online.target

[Service]
ExecStart=/usr/sbin/strongswan start --nofork
Restart=on-abnormal
RuntimeDirectory=strongswan
RuntimeDirectoryMode=0755

[Install]
WantedBy=multi-user.target

It should not require renaming ipsec, which indeed belongs to libreswan package. That is official part of RHEL8 (CentOS8 Stream), which should not be modified by strongswan package. It should allow both installed at the same time.

from strongswan.