Recommended and mentioned products
Convenient End-to-End Encryption for E-Mail
A browser extension to verify the authenticity of websites
Deploying via IPFS might work indeed, but you're then either reliant on a gateway or have to run IPFS yourself locally. I know that Brave now supports IPFS, but for most people a more lightweight solution would be to install the Signed Pages extension for Chrome or Firefox. I'm not sure if you actually need a trustworthy backend, or rather, if the frontend is encrypting its state before sending it to the...