depth=2 O = Digital Signature Trust Co., CN = DST Root CA X3
depth=1 C = US, O = Let's Encrypt, CN = Let's Encrypt Authority X3
depth=0 CN = server.host.com
verify return:1 Verify return code: 0 (ok) QUIT
where we'd take note of the Verify return code: 0 (ok) status. The "code: 0" is good, it means the certificate is correctly signed by a certificate authority. I usually type "QUIT" to exit the current connection (this is a client connection to Apache, so you could create a request here). Else some systems might need ctrl-d to send an "end-of-file" character to close it.
But if you see:
Verify return code: 18 (self signed certificate)
then it means the certificate could be self-signed (you created the cert/key yourself), or the ca root bundle or chain have not been correctly installed.