I'm still pretty green so I'm not sure what terminated means in this context.
My domain registrar for my "pretty" domain (not FreeDNS) allowed me to issue a Let's Encrypt on it. It gave me the encrypted Cert code, Private Key code, and Immediate Cert code. I was able to bring them down into .crt and .key files respectively and assign them to my NAS. Jellyfin though required a PKCS #12 file so I installed openssl CLI via Choco and fed it my .crt and .key files to generate the necessary pfx file. So, right now all the cert information is tied to my "pretty" domain via my domain register. I would assume that my register and Let's Encrypt has my private key info, but also my key files uploaded to the NAS and rolled into the PFK file.
Not sure if that helps or answers your question but that's the info I got.