Due to russian war in Ukraine there a lot of sanctions. I'm personaly agianst this war, but live in ru now. Is supporting EU project allowed to russians users? I mean, my boinc client works fine. But is this legaly ok for me to help EU projects? Sorry if this question is too silly, I'm really bad in EU laws.

Supporting some random European universities and research institutes shouldn't be illegal. If you were a corporation, then the sanctions might apply if they sanctioned compute itself from being exported. Since you're just a person, there should be no problems (also you're not being paid, this is volunteer work).

I hope this message finds you well. I recently learned about your generous contributions to European universities and research institutes, and I wanted to share my thoughts.
While your intentions are undoubtedly commendable, it’s essential to be aware of potential risks. International regulations and sanctions can be complex, and even seemingly innocuous actions may have unintended consequences. Your friend’s experience serves as a stark reminder of this reality.
As individuals, we strive to make a positive impact on the world. However, I encourage you to stay informed and consider the broader context. Perhaps researching specific guidelines or seeking legal advice could provide clarity on the matter.
Thank you for your empathy and commitment to being a good human. Let’s continue supporting constructive initiatives while remaining vigilant.

Wishing you safety and success in all your endeavors.
Alexander "God bless the world" (*or what you believe in)