I have exactly this problem albeit almost 144 days later than the reddit posting - https
/www.reddit.com/r/nexus6/comments/3ucizf/how_to_clear_the_default_browser_on_marshmallow/
- and cannot find a fix yet, other than the workaround suggestion to download another browser from Play and hope it’s one that will clear the hierarchy browser default back to “No default browser”. Keep in mind that not every and all choices will do it, so my suggestion is to download the lightest weight browser one at a time [like 1.75 - 2.25 MB] so if you don’t see it clear the default you can uninstall quickly and go on to the next one. One way you can tell immediately is if you tap on a link and get a pop-up menu, it will be a choice between the default browser and the newly downloaded browser, but not show your other browsers yet or go to your Configure apps page and check for ‘No default browser’
I should think that in Settings>Apps>Advanced>Defaults>Browser, the menu should include 'Android System', or ‘No Default Browser’ or some choice to clear this hierarchy setting to bring back the pop up choices' menu when tapping on a new link. Default settings in the individual browser apps mean… well what are they for, exactly? I’m not allowed to use them the same as I’m not allowed to clear the default on the hierarchy ‘Configure apps’ page.
What’s even more disturbing for me is that now I’m not allowed to receive incoming calls on my magicJack app because the hierarchy default setting for Phone, is Phone, meaning cell phone and no other choices even appear at all. Therefore, when somebody calls my magicJack number, the UI for magicJack lights up my screen as it rings 1 time, then goes dark and my cell phone UI lights up my screen as it is ringing a 2nd time. When I answer, I’m burning expensive cell time minutes instead of magicJack over WiFi. To date, I have to tell people I’ll have to call you right back as outgoing calls stay magicJack. I haven’t found a workaround for this yet except to get back to KitKat so that it is my phone again.