Please use PlatformIO instead of the Arduino IDE 2.0 beta. In PlatformIO, all boards are supported and debugging etc. actually works -- we don't have it setup yet for Arduino IDE 2.0 instructions regarding e.g. debugging, so the experience will be poor. The Arduino IDE 2.0 is a modded VSCode version anyways, better use the real thing directly.
I can confirm that when you add our package URL to the "Additional Board URLs", our "GD32 ARM Boards" package won't show up.. likely due to missing checksums and length field in the manifest?
If I install the GD32 package in the regular Arduino IDE 1.x, and then open Arduino IDE 2.0, the package is there. So it just seems to be a problem with stricter installation rules for the 2.0 IDE? Compilation works.

So if per https://arduino.github.io/arduino-cli/0.19/package_index_json-specification/ the fields size and checksum are mandatory, we have a chicken-egg problem if the index file package_gd32_index.json lives in this repo. If we'd like to make a release, we have to generate the archive for the board package (aka this repo) and its checksum and write the length and checksum into the package_gd32_index.json file -- which however also lives in this repo. So now we've modified the file inside the board package repo which again changes the checksum. If we regenerate the checksum and write it back we get to the same point. The file in which the checksum is written musn't be part of the checksummed data, it needs to be in a different repo. At https://github.com/arduino/Arduino/wiki/Unofficial-list-of-3rd-party-boards-support-urls I see they've done this for other cores too, disconnect the index file from the core repo. While we can do this to enable downloading the latest master branch version, it'd be good if the Arduino IDE 2.0 installation logic allowed to ignore the length and checksum fields to get a "bleeding edge" version.. I'll see if I can open an issue about this

Can't searched gd32 borad in arduino2 IDE board manager #52

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