We are going to implement Office Online Server to allow users to view documents in the browser. They should not see any of the buttons like "Share", or "Embed". E.g. for sharing, this results in an error, as we have disabled Sharing on the document library level. However, the button is still visible...
I've tried to add custom JS/CSS, but as far as I can tell this is not possible. The actual ASPX page is a layouts page, and as far as I can see, it does not use a master page. So I can't add CSS/JS. I haven't tested adding CustomActions but I don't think that will work?
So question is: How can I hide the buttons in Office Online Server for SP2016 On Premises?