We have released a partial fix to the app store with version 3.18054.28. I say a partial fix as you can now go offline on the app list and it keeps the downloaded apps in the app list when reopening PowerApps while offline.
The scenario that is taking us longer to address is when going offline while PowerApps is closed in which case the app list still appears empty. Thank you for your patience with this!
Is there any update on this issue or an eta for a full fix? The issue is marked as solved but the given solution is only partial. I can't consider powerapps to be truly offline available if you're required to first start the app when online.