Ubuntu and other Linux-based are not supported

[N0rbert]

I have just bought great nice-looking Sipeed Longan Nano - RISC-V GD32VF103CBT6 Development Board with Acrylic Case .

I have already installed Arduino IDE 1.8.16 on my Ubuntu MATE 18.04.6 LTS amd64 system; then I have added below URL to Boards Manager
http://bigbits.oss-cn-qingdao.aliyuncs.com/Arduino_for_GD32V/package_longduino_index.json

Then got error red message Tool gd32vflash is not available for your operating system.:

Please add support for very popular Ubuntu and other Linux-based systems.