Hi @chris,
You can’t replace /etc/exim4/exim4.conf.template with a “fresh” exim4 conf from /usr/local/hestia/install/deb/exim/exim4.conf.4.95.template because if you use dovecot and sieve that file must be modified.
A few days ago I generated a conf file for Exim 4.96 in Debian 12 with dovecot, sieve and spamassassin but it will work too for Ubuntu and Exim 4.95 with dovecot, sieve and spamassassin .