[mmalone]

Good question. I know you can add a root CA cert.

I’m on iOS and don’t have an Android or ChromeOS device handy. I don’t see a way to remove a cert from Apple’s iOS trust store (settings just tells me what store version I’m running). There may be a way to do it using mobile device management (MDM) tools.

[SAI_Peregrinus]

On Android (Galaxy Note9 in my case), you can disable any CA certificate from being used. There's a "view security certificates" screen with the ability to disable each individually.