These flashcarts, and their clones sold online, use the EvolutionOS kernel. This is a highly-compatible kernel that can run almost all games, romhacks, and homebrew, and also comes with extra features not commonly found in other carts, like Real-Time-Save and an in-game menu.

Clones of the DSOne SDHC were common on AliExpress and eBay, however they had a somwhat high dead-on-arrival rate.

Using YSMenu is only recommended if your DSOne has a PSRAM error and cannot use EOS. To check if your DSOne SDHC has a faulty PSRAM, hold L and R on boot to run the DSOne’s self-test. The self-test feature was removed on the DSOnei.

There are ways to fix a faulty PSRAM, however, it requires access to soldering tools. A video showing the process can be found here: https://www.bilibili.com/video/BV1Ab411Z7hq/

More detailed information about setup and usage can be found in the DSOne Manual GitHub