I am running CentOS Linux release 7.9.2009 (Core). Is there a way to configure Let's Encrypt
Certificate Authority (CA) in CentOS 7 to create digital certificates for servers on LAN or for VPN clients that need SSL Certificates.
Yes, but only if you "own" (can adjust public DNS records for) mydomain.com. You'll be using the dns-01 challenge type and need to be able to create a TXT record for _acme-challenge.gitlab.int.mydomain.com that is queryable from the Internet.