I bought a pricey board on aliexpress which appears to be well designed and of decent quality with a ton of io pins. It gives you 8 Mb SDRAM (on a 16 bit bus) and 16 Mb of QSPI flash in micropython. If you need heavy graphics or just a big heap it's maybe worth the price.
It seems to be primarily (or solely if im honest) made for Universities in China and is very well documented (980 pages pdf) + 700 Mb software, but if you're running micropython and don't understand Chinese it's all worth nothing. In fact it's impossible to download the documentation without help from the seller.
But after receiving the board I spended a few hours of hacking with 谷歌翻译 (google translate) and everything was surprisingly up and running. The ethernet code is not tested yet since I'm still waiting for a RMII transceiver. The only downsides I found so far is the USB is only running in FS mode (needs an external driver for HS mode) and the board has a special SWD connector (they sell a CMSIS DAP compatible debugger with that connector). I can't see why a st-link would be fine, although I have not tested it.
https://www.aliexpress.com/item/3292578 ... 4c4dXCQSBI
https://www.aliexpress.com/item/3292364 ... 4c4dXCQSBI
I will be happy to upload the definition files to github if anyone wants to try it out.