I would guess it could work, but speed might be an issue: routing the traces on a PCB, and the added capacitance of multiple flash chips might cause problems.
I think this would be a one-off, or a low volume trial, so designing and populating a custom pcb would almost surely be more expansive than 3 off the shelf boards. Maybe you could try stack the flash chips on top of each other, and use some switch to select one. Maybe just switching the CS might work. Or might not. No idea honestly.
For ESP32, most likely it would be cheaper and easier to just use multiple low-cost devkits. Just leave it in the breadboard with the circuitry you are working with. Unless your goal is to try to solve the same problem in the same circuit in different languages. But still, you can pull the whole devkit.
For STM32 external flash would be harder, because I think only high-end ones have only external flash. But just replace the cpu-board, if you work with Nucleo boards, or some other lowish-cost option (you can get ~4€ F401, or ~10€ F407 STM32 boards from aliexpress)
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I would guess it could work, but speed might be an issue: routing the traces on a PCB, and the added capacitance of multiple flash chips might cause problems.
I think this would be a one-off, or a low volume trial, so designing and populating a custom pcb would almost surely be more expansive than 3 off the shelf boards. Maybe you could try stack the flash chips on top of each other, and use some switch to select one. Maybe just switching the CS might work. Or might not. No idea honestly.
For ESP32, most likely it would be cheaper and easier to just use multiple low-cost devkits. Just leave it in the breadboard with the circuitry you are working with. Unless your goal is to try to solve the same problem in the same circuit in different languages. But still, you can pull the whole devkit.
For STM32 external flash would be harder, because I think only high-end ones have only external flash. But just replace the cpu-board, if you work with Nucleo boards, or some other lowish-cost option (you can get ~4€ F401, or ~10€ F407 STM32 boards from aliexpress)