I have a working access point on a rspbi, works perfectly with my captive portal on ios and os x based machines.
But android does not popup a captive portal, and I can see the requests for clients3.google.com
The way I do the captive portal is by redirecting port 53 (udp) to my apache server, and there display the login page for the access point.
Any ideas why there is no automatic popup? I already checked the chromium project page and it looks like I did everything right.