but the maintainers have not made it compatible for use with Arduino IDE 2.x:
So if you want to use the Roger Clark STM32 boards platform, the easiest way to accomplish that is to use Arduino IDE 1.x (which can be downloaded from the "Software" page here).
If you want to use the modern Arduino IDE, then use the "STM32 MCU based boards" platform (AKA "STM32duino"), which is fully compatible with Arduino IDE 2.x.