the compatible chips are the stm32f401, 411, 412, 413 and 423
I've also got a few 413's on the way from digikey (since i can't find those on aliexpress).
The're really insane 0_0 1.5Mb flash, 320kb ram, dacs, plenty of spi i2c i2s, you name it, sdio, usb host, .... it's all there in that tiny chip that fits on a bluepill/maple mini /...
There usually is 1 small difference with the pinout of the stm32f103: they have one output pin less, because one of the pins you're supposed to put a capacitor on for the internal reference voltage. but if not using that feature, you probably don't even have to bother
(and otherwise it'll be like adding the bluepill parallel resistor for usb).
also if we'd convince a chinese factory to produce boards like this, they might want to swap out the qfp pad for something more suited for qfn
. it fit's on there, but it was not really made for it XD.
and you can indeed find some mucleo's 401 on aliexpress etc... but it's again a stupid uno sized board, and 20$ is just too much for such a clumsy thing >_<.
you can indeed find the 401 for about 4-5€, and the 411 for 5-6€ a piece, so making a modded bluepill/maple mini isn't that expensive XD.
And a maple mini with the better chip is indeed also possible
. In my previous dealings with the boards however (a while back i did the same with an stm32f303 on bluepill/maple mini) i noticed that the baite pcb is a bit more delicate to switch the microcontroller on. and since it costs a lot more, i stuck with bluepills from then on. With my SMD rework station it may work better now, i'll give it a try (finally a usage for all the maple mini, bluepill, blackpill, ... boards i've been hoarding XD)