Russia bad, I get it. But this is ridiculous.
The flipper zero is using off the shelve components and the firmware is open source. What more do you want?
You don't need to use the android app if you are worried about malicious future updates.
All the possible scenarios he lists could just as well happen to a US based company like being pressured under the patriot act to alter the app and collect keys.
Having a device built by actual hackers appeals to me way more than some coorperate gadget.