To add the boards fro the links in this page, the link has to be placed under File->Preferences->Additional Board Manager URL:
Then the board can be added through
tools->board->Board Manager.
For the LGT8F family boards:
https://raw.githubusercontent.com/dbuezas/lgt8fx/master/package_lgt8fx_index.json
Adafruit compatible bords:
https://adafruit.github.io/arduino-board-index/package_adafruit_index.jsonhttps://adafruit.github.io/arduino-board-index/package_adafruit_index.json