Are micro controllers like espruino or others usually unencrypted? thanks

hi,
i am completely new to the MCUs.

just wanna ask are things at this level, are usually not encrypted?
because several years ago, some made a smart gun that help you to shoot.
it runs on android unencrypted.
someone found that one can take out the IC, and flash evil roms so that you think you are shooting the bad guy, indeep shoots the good guy.
their solution is to encrypt the rom.

i understand that NOT everything should/will be encrypted,
like i dont expect a CASIO calculator be encrypted (but it wont hurt if it is).
i am still exploring what espruino/bangle could do in my life
so i wanna ask this at the beginning.

yah, i am new to this world where 256KB RAM means a lot of RAM.

thanks

ref:
https://www.popsci.com/smart-rifle-software-can-be-hacked/