The only solution you'll have is either assigning a trusted certificate to the Captive Portal via an SSL/TLS service profile or you'll need to simply have the guest users bypass the certificate warnings. The best solution would be getting a trusted certificate from an external CA and configuring the Captive Portal to utilize that.
Click Accept as Solution to acknowledge that the answer to your question has been provided.
The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!
These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!
The LIVEcommunity thanks you for your participation!