lemmy.ml is part of Lemmy development as it is used to test new versions before release, take performance measurements and have first-hand experience with the mod tools. And in any case the server is already paid for, so all donations now go to developer salaries.

Edit: Additionally lemmy.ml hosting is only funded via Opencollective, so if you donate through any other platform the money goes entirely to developer salaries.

Which red flags do you mean? Is there a better way to ask for donations?