I'm working on SP 2016 Enterprise on premises with the April release of Office Online Server.
That all works and documents open in the browser.
Now I want to exclude a single document library from that behavior. The document library has a custom content type and document template that uses smart parts - these don't work in Office Online Server.
set the document library setting 'Opening Documents in the Browser' setting to 'Open in client application' - no effect
activated the site collection feature 'Open Documents in Client Application by Default' - no effect
The clients are Windows 7, IE 11 and Office 2010. Chrome exhibits the same behavior - documents always open in Online Server.