Did you all miss TheNiceRansomware ? https://github.com/agentzex/The-Nice-Ransomware
This new edition, should work on all Android versions (not tested though, and I also really don't recommend on testing on anything other than VM/AVD), using Android NDK.
This project is meant to be used for educational purposes only, that's why this time, I left most of the malicious code out of the repo. If you wish to have the complete code, please contact me and explain who you are and what is your goal, but bear in mind that I will release it only for people I know. Thanks for your understanding :)
Blog post - https://whiterosezex.blogspot.com/2019/07/theniceransomware-android-ndk-edition.html