Download the certificate from Nebula for Android device

My private home network uses wpa3 enterprise with nebula cloud authentication. My linux laptop can authenticate only when I choose not to require a CA certificate. My android phone running grapheneOS doesn't have this option because the OS is security-focused and this is a well-known security flaw which allows for man-in-the-middle attacks. Previously I could authenticate on my phone by choosing 'trust on first use' in the CA certificate field, however I had to do that every single time I wanted to connect to the network. For the past week or so I cannot even do that as I get the error in the title.
I would like to know a) where I can access Zyxel's CA certificate to install on my device, and/or b) when we can expect Zyxel to address this for cloud authentication.