Will expo publish continue to work (with release channels) after expo build is discontinued Jan 4 2023? Is there any single place we can read about all the changes that will apply to the build and ota process?
Classic updates will probably be disabled at some point, but there is no timeline for that yet.
To migrate to EAS Build I recommend starting on intro page EAS Build - Expo Documentation
In most cases just running
eas build should work.
You can still use classic updates on EAS Build
Migration from classic updates to EAS Update is described here Migrating from Classic Updates to EAS Update - Expo Documentation