I use specific groups within KeyCloak to define what applications I want a user to see. However, I am using Cloudflare Zero Trust and passing the group claim.

The way I see it, using their Zero Trust tunnels and such, the benefits out weigh any perceived threat from them. They handle so much traffic anymore, my little bit of data isn't even going to be a small blip in their infrastructure. They assess the traffic for threats on the fly, they aren't going to attempt to keep a copy of everything their system see's, that would be just way to much to deal with. Hell of a lot better than a marketing company (Google) holding your email and the like.