Question about low-cost Chinese STM32H750 boards from Ebay, Alibaba, etc.

I'm new to ARM, so I want to have a play with them by building a POV globe.  It requires 380k_bytes of memory, so I have chosen the STM32H750 as my platform.  When I first came across these boards on Ebay for £20, I searched for info about them, and I think I read somewhere that they can't be programmed through the USB, though I notice that they have a CH340C USB-Serial chip on them.  If they can't be programmed that way, can program be transported to them on the SD card?    I can't find any specifications for them on the web, but on the face of it, they look like a good solution to getting me started on this chip.  I think I also read that they can only use one SPI channel, which would be a problem for me - but wherever I read these things, I can't find it again, and I'm not sure exactly what I did read.  

Can anybody give an appraisal of these low-cost Chinese STM32H750 boards that are available on Ebay, Alibaba, etc?

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