There’s a Support page (linked from “Support” at top of this website). On that page is a link to Player Reporting: https://support.ageofempires.com/hc/en-us/sections/360011472111-Player-Reporting
I don’t know if AoE4 has an in-game reporting mechanism, but the page I linked to mentions you can submit a request to contact the team. If that doesn’t work, or if that page hasn’t been updated to be able to reach AoE4 support (even though I clicked the AoE4 support page), you can see the quote below as potentially beneficial info in your endeavor.
Note: If you’re trying to call out the player in your screenshot, you’re not really supposed to do that per the forum’s Code of Conduct. The quote is below, but so is the additional support info I mentioned above:
Age of Empires Forum Code of Conduct and Terms of Service
DON’T…
Call out other players in threads. If you have an issue, take it to PMs or contact us directly at AoESupport@microsoft.com.
Just trying to provide some info that may be helpful