Thats a bad/broken bit.ly URL that has been broken for ages.
Try:
- Download the Developer Rig for Windows, Mac, or Linux, then open the downloaded file to install the Rig:
Linux*: https://developer-rig.twitchcdn.net/Twitch+Developer+Rig.AppImage
MacOS*: https://developer-rig.twitchcdn.net/Twitch+Developer+Rig.dmg
Windows*: https://developer-rig.twitchcdn.net/Twitch+Developer+Rig+Setup.exe
From End of support for the Twitch Developer Rig - Announcements - Twitch Developer Forums
instead