If you haven’t seen the following discussion thread, you should take a read through it. Much discussion on installing alternate OS’s, including Debain, to the single bay My Clouds.
User Fox_Exe has some directions on installing Debain to a second gen single bay My Cloud which may or may not apply to what you seeking to accomplish.
https://fox-exe.ru/WDMyCloud/WDMyCloud-Gen2/Debian/
Howto_en.txt: https://fox-exe.ru/WDMyCloud/WDMyCloud-Gen2/Debian/_howto_en.txt
Howto_ru.txt: https://fox-exe.ru/WDMyCloud/WDMyCloud-Gen2/Debian/_howto_ru.txt
