I admit, that's a solution, even if a very unpleasant one: Installing a custom root CA is intentionally complicated, so this is hardly doable as an onboarding experience. The setup must be repreated for every single client device that should access the server.

There remains the question how I would get the CA certificate onto client devices in the first place.

Lastly, with asking consumers to install a CA certificate, I ask for a significantly more powerful permission than if I could just have them trust my certificate. This seems like a step backwards security-wise.

That is also an insane and unrealistic suggestion.