Warning: I made this.
As a 200kHz oscilloscope I don't think it's worth much, but as a CH32F103-based Blue pill development board in a nice case with a high-bandwidth screen, battery and charger and USB-C, it's potentially pretty useful.
I've since found out that Fnirsi make the DSO153, which is an upgraded model with signal generation support. This looks similar but has a different microcontroller and a more complex board and, obviously, an output analogue stage. I can't get a good picture of what the microcontroller is but it's likely to be an upgraded CH32F. It's another $10 more expensive, which takes it out of the sub-$20 sweet spot of being-cheap-enough-to-buy-as-a-component that the DSO152 is in, but if anyone does want to build a custom diagnostic tool it might still be worth a look...