Uhm a desktop client is useful?
I think that the web version is perfect, maybe a mobile version is better.

by Desktop client i mean : Android , IOS , Mac , windows , Linux :)

The client is meant to provide offline access.

Maybe create a web version that use Service Worker to cache the pages.

That won't solve the offline availability on mobile issue.

Service worker work also on mobile but to have a client that works everywhere we need a web version.

Or use qt5