End-to-end encrypted static website content

I have a really simple static webpage which just consists of a single html file that gets served.

I want to encrypt some of its content so it can only be read by certain persons (the ones that know a certain passphrase). Please note I don't want to encrypt the source code. Just a "secret" content inside of it.

For instance:

<p>
This is a secret message
</p>

I know I can add authentication at a server level, but I don't want my html file to be even readable by the server, meaning I want end-to-end encryption of the "secret" parts.

This might be a good job for asymmetric encryption. I could use the others public keys to encrypt the message so only them will be able to read it (I even thought of mutual SSL authentication).

The thing is, this might be too difficult/not possible to do for the intended recipients as they're non-technical people. I just want them to use a passphrase to see the "secret" content, not installing any certificates or similar stuff. So maybe just symmetric encryption is a better fit.

Do you have any ideas on how to achieve this? Is AES or a similar algorithm a good idea for this?

I'm open to different approaches.

Thanks