First reported on 22 October 2020 IST (https://t.me/BotTalk/357429) by @adityaruplaha (myself :P)
(haven't got around to filling this yet, please check the messages in the linked chat)
This code example demonstates how to use LoginUrl
in a UserCommand
to work-around Telegram Login Widget not working on certain browsers.
It uses PHP with the official Telegram PHP Bot API, but other languages should work similarly.
The user gets a prompt if they want to login, then the callback URL opens up with the required parameters, if the user accepts. Otherwise, it gets opened with no parameters. You can then handle it accordingly. Check https://core.telegram.org/bots/api#loginurl for details.