/usr/share/strongswan/templates/config/plugins/ is in libstrongswan-extra-plugins 5.6.2-1ubuntu2.3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/strongswan/templates/config/plugins/acert.conf
/usr/share/strongswan/templates/config/plugins/af-alg.conf
/usr/share/strongswan/templates/config/plugins/attr-sql.conf
/usr/share/strongswan/templates/config/plugins/bliss.conf
/usr/share/strongswan/templates/config/plugins/ccm.conf
/usr/share/strongswan/templates/config/plugins/chapoly.conf
/usr/share/strongswan/templates/config/plugins/cmac.conf
/usr/share/strongswan/templates/config/plugins/coupling.conf
/usr/share/strongswan/templates/config/plugins/ctr.conf
/usr/share/strongswan/templates/config/plugins/curl.conf
/usr/share/strongswan/templates/config/plugins/curve25519.conf
/usr/share/strongswan/templates/config/plugins/dnscert.conf
/usr/share/strongswan/templates/config/plugins/gcrypt.conf
/usr/share/strongswan/templates/config/plugins/ipseckey.conf
/usr/share/strongswan/templates/config/plugins/ldap.conf
/usr/share/strongswan/templates/config/plugins/load-tester.conf
/usr/share/strongswan/templates/config/plugins/mysql.conf
/usr/share/strongswan/templates/config/plugins/ntru.conf
/usr/share/strongswan/templates/config/plugins/pkcs11.conf
/usr/share/strongswan/templates/config/plugins/radattr.conf
/usr/share/strongswan/templates/config/plugins/rdrand.conf
/usr/share/strongswan/templates/config/plugins/soup.conf
/usr/share/strongswan/templates/config/plugins/sql.conf
/usr/share/strongswan/templates/config/plugins/sqlite.conf
/usr/share/strongswan/templates/config/plugins/systime-fix.conf
/usr/share/strongswan/templates/config/plugins/test-vectors.conf
/usr/share/strongswan/templates/config/plugins/tpm.conf
/usr/share/strongswan/templates/config/plugins/unbound.conf
/usr/share/strongswan/templates/config/plugins/whitelist.conf