Like the new IDE! How can I add a new architecture to the IDE. I want to add the Aurix boards (ShieldBuddy TC275 and TC375) to the IDE. Is there some some kind of guide to doing this? For the old IDE there was an application note available. I used to cheat with the old IDE and just copy the CPU-specific stuff into C:\Program Files (x86)\Arduino\hardware and the IDE picked it up with no problems. The equivalent trick ("C:\Users<usename>\AppData\Local\Arduino15\packages\arduino\hardware") does not work with the new IDE.
There is one here for the recommended Boards Manager installation method:
It is incomplete though because it only describes how to install the official Arduino boards platforms. When installing 3rd party boards platforms, and additional step is required, which is to add their package index URL to the "Additional Boards Manager URLs" field in File > Preferences, then restart the Arduino IDE.
Arduino IDE 2.x does not have bundled boards platforms like the classic Arduino IDE. It instead uses the Boards Manager system to install the "Arduino AVR Boards" platform of the Uno, Leonardo, Mega, etc. boards on the first run of the IDE.
It would be the same in the classic Arduino IDE. There is an extra version folder level for the platforms installed to that location. For example, you will find the Arduino AVR Boards platform at this location:
Notice the extra level of folder depth for the 1.8.4 folder.
But C:\Users\<usename>\AppData\Local\Arduino15\packages is typically only used for the automated installations via Boards Manager. For manual installations, the preferred location is the hardware subfolder of your sketchbook folder. If you don't know where your sketchbook folder is, you can open File > Preferences in the Arduino IDE and check the path shown in the "Sketchbook location" field.