NuttX runs on the ESP32[1] which provides a rather featureful shell[2] as well as a file system.

[1] https://nuttx.apache.org/docs/latest/platforms/xtensa/esp32/...

[2] https://nuttx.apache.org/docs/latest/applications/nsh/index....

Someone had managed to run Linux on ESP32 in 2021 [0][1]. But that's more of a proof-of-concept rather than a usable thing. Not much information besides that so far I think.

Update:

From the post [0]: someone also managed to run Ubuntu 9.04 on the board in 2020 [2].

[0] https://www.cnx-software.com/2021/07/18/linux-5-0-esp32-proc...

[1] https://www.esp32.com/viewtopic.php?t=2681

[2] https://old.reddit.com/r/esp32/comments/dtlj7n/booting_linux...