Raspberry pi/small NUC with a screen, in a digital kiosk mode. Just load a static html file with some js to update the clock. No keyboard, no touch input, no way to break it. Connect to it via ssh over tailscale or wireguard VPN to update the HTML with the notes you’d like to display. This way if internet goes down, the clock still works and whatever was displayed wrt messages stays displayed, and you don’t have to worry about the increased overhead of home assistant changes or updates breaking things. It will remain consistent since it’s just HTML and js. If you want less technical family members to be able to update the display…idk, seems like a headache.

As others have suggested I would stick to internal only until you’re comfortable. Dealing with automated port scanning from all over the globe is a nightmare if you aren’t running a tight ship, and a collasal headache to deal with if they get in. I started with pihole, jellyfin, and some other simple docker services. Check out linuxserver.io if you go the docker route, they have good prebuilt compose files for you to use and the community has good info on their forums. You don’t need a domain but it’s preferred if you want to host something public-facing. Make sure you have fail2ban configured if you open stuff up to the web, it makes dealing with the automated attacks easier.