Here’s an article on how you can prevent printscreen from taking screenshots. I assume scammers did this and got the seed phrase. This applies to awindows, maybe there’s something similar on Linux?
It may not be foolproof. Using C++, I have written code that takes a screenshot which was useful for reporting. I’m not sure whether my code would still work. Unfortunately, my graphics card has died on my pc so I can’t test this.
Assuming that printscreen was involved when coins were lost, this action will close a security hole.