Popping a shell on BittBoy or other Linux based retro emulators

[stretch]

Hi I'm new to the forums and looking into the existing retro consoles on the market to see which could be used to gain shell access to the underlying operating system.
Looking on AliExpress and eBay suggests there are multiple consoles, such as the BittBoy, Pocket Go, HeyNow and the GDK, amongst others like them that have the ability to load games from SD card and even load a separate OS from the cards as well (according to their marketing it's a "DIY Linux OS", that's all they say). With this in mind has anyone managed to gain shell access or looked into it?

I understand this many not be the best place to discuss this, since this forum mostly aims to make retro emulation consoles and this is using the emulation console as a stripped down computer. However any insight would help!

Thanks!