Linux required an MMU at inception[1] and currently requires an MMU. Instead you have μClinux[2] which although it is integrated with the mainline kernel since 2.x, it lacks some important features, like it has neither fork() nor autogrow stacks[3].

[1] https://www.cs.cmu.edu/~awb/linux.history.html

[2] https://en.wikipedia.org/wiki/ΜClinux

[3] https://www.eetimes.com/how-uclinux-provides-mmu-less-proces...