Presenting a different Captive Portal to different Browsers

Question: is it possible to verify Google users via a captive portal linked to Google user directory  and Microsoft users via Captive portal linked to MS user directory?

In order to tackle this question we need to brake down the requirement a little and understand what would dictate a user is wanting to connect to a Microsoft Account vs a Google account. in the case that the google accounts all use Chrome as the browser and the Microsoft accounts all use Edge then there is a key difference that we can detect at the firewall during the HTTP session. The  HTTP ‘Client User Agent’ presented by the browser.

So in order to match a specific policy we can use this along with a tag to match devices that we know need to be authenticate for web access. e.g 

We can then create two separate Policies each with the corresponding Captive portal app linked to either Google or Microsoft respectively.

Captive Portal configured to authenticate with Google Account
Captive Portal configured to authenticate with Microsoft Account