Just to make sure: if the company goes bankrupt, will I be able to continue releasing updates etc.?

The Expo Updates protocol is an open standard specified here https://docs.expo.dev/technical-specs/expo-updates-1/

The hosted services offered by the Expo team called EAS has an implementation of an updates server that conforms to that protocol. If EAS went away or you wanted not to use EAS, you could write and operate your own server that conforms to the protocol instead.

The Expo setup that I use never calls into Expo servers at build time. For OTA updates, I've managed to get my self-hosted Expo update server working too, although I'm not using it at the moment, as its incompatible with the React Native New Architecture (it's the last expo package to lack this support - hopefully they'll add it soon).

Do you have the self hosted OTA open-sourced? I tried implementating it, but it didn't work for some reason.

Unfortunately my update server contains a bit more stuff which I'm not planning to clean up at the moment, but the logic of the update server really is taken right from their https://github.com/expo/custom-expo-updates-server repo. Perhaps you were blocked by this https://github.com/expo/custom-expo-updates-server/issues/12 ? If so, its been fixed in the meantime, perhaps it works for you now?

please do so, I would like to build it totally local and when I realize that outsourcing the build to the EAS cloud saves more time and money I will switch later, that sounds like a nice way to get more people use Expo.

I've put a link to it on my other comment. Hope it helps.