Maybe some, but certainly not all in the list. Neither Ryanair nor Wizzair need app, you can do everything in the browser.
481 karma · joined December 19, 2019
This does not imply that it is easy to track everyone everywhere at all times. I guess most targeted ones would like to protect their communication, and even meetings in person are possible if you keep some safeguards.
If you develop for a diverse set of user you need a lot of effort.
https://delta.chat/en/help#how-can-i-ensure-message-end-to-e...