I am working for Canadian company Evertz Microsystems, actually Evertz AV group.
We would like to have our own intermediate CA which is signed by the public CA. Do you provide this service and how much it costs?
From what I see your root certificate is in Firefox trusted list but I could not find it in Chrome’s. Do you know if Chrome is adding your root certificate to their trusted list any time soon?
First of all, I believe that currently Let's Encrypt (or ISRG) does not provide external certificate signing (do not sign intermediate certificate. (As @_az already said)
Firefox (Mozilla) maintains a list of their own CA trust program that's used in their browser. But chrome (itself) doesn't operate a CA trust program, their certificate trust source comes from the machine's own certificate store. (Like Microsoft trust program). For compatibility please refer to this link: Certificate Compatibility - Let's Encrypt