Can you do that on webpages (which is what equinox.space is) without first pushing play or unmuting them? I know on youtube you have to unmute it first. I don't really go to any other music or video websites on my phone, so I'm not sure if they're all like that or not, but in my experience, webpages respect the ringer side button unless something is clicked to override it.

Sure, within the website I have to unmute it and up my volume to hear anything, but it's still playing without me having to switch off the physical DND mode button on the side of the iphone. My phone remains in DND mode and I still have no audible notifications.