Nextcloud and Onlyoffice SSL

Hi I’ve recently setup an OnlyOffice instance to add to my Nextcloud. It all works perfectly although I have a question. My Nextcloud instance runs behind a reverse proxy with SSL. Initially when adding the OnlyOffice instance to Nextcloud I had a mixed content error thrown when adding the server address. I got round this by adding a self signed SSL certificate to the OnlyOffice server which then allowed me to add the link to Nextcloud without an error.

However what I’ve then found is that for OnlyOffice to work I must first add the SSL certificate to the browser of any device I want to use OnlyOffice on. Otherwise trying to open documents from Nextcloud throws an unable to reach OnlyOffice error. For now I’ve got round this by setting up a subdomain for OnlyOffice and adding it to my letsencypt SSL certificate.

My question is has anyone else found a better way round this issue? At the minute if I were to give out the URL anyone could use my OnlyOffice server which I’d rather avoid.