At least hidden profiles would be good enough for basic protection.
They have this which wipes your device, but you can get killed under duress. https://discuss.grapheneos.org/d/14722-using-duress-password...
In fact, a core aspect of security is having access to a feature in the very first place.
A forum, being hosted on the web has absolutely no reason to stay away from the de facto scripting language of the platform. What would be your threat model for that forum? A zero day that would break the whole world?