lemmy.world is run by the same people as mastodon.world and it is already donation funded. They post financial updates on their blog: https://blog.mastodon.world/

they have been funded by grants from NLnet (I think from EU funds?) but I think are transitioning to donation-based.

the lemmy source code is public

hexbear is currently running an old version of lemmy that doesn’t support the v3 API or federation. migration to a more modern lemmy is in progress

And I think the biggest performance boost would be to separate the application and postgresql onto different servers.

I think hexbear.net (an older lemmy fork-ed site) is working on this in conjunction with moving back to a modern lemmy version

Cloudflare does have the ability to spy on traffic though, they hold SSL keys.

A better option for a simple usecase like that is using something from your DNS provider. Depending on who you use they may have a health check service that has no access to user data that can simply ping a URL, and if it fails hard enough, start redirecting traffic to join-lemmy.org

I think Constellix has it, though I’m not necessarily recommending them specifically