Hello everyone,
The SSL certificate on the lab.gamebuino.com site expired on August 12, 2021.
This subdomain of Gamebuino hosts (among others) the Gamebuino META card descriptors for the Arduino environment. (https://lab.gamebuino.com/arduino/package_gamebuino_index.json)
We are on the spot, but while waiting for everything to be in order, you can use this alternative repository:
https://gamebuino.com/sdk/package_gamebuino_index.json
Sorry, for the inconvenience sic;).