I believe I have contributed in the past. I use a check or my credit card to contribute to many organizations. Yours is about the only web-site I know that does not give a method for donations. I have declared my love of Wikitree and one of the things I love most is that it is FREE. I am willing to contribute in a small way to keeping it that way!
I am not wealthy. My typical contribution to non-local groups is $100. I religious disagreement (Presbyterian vs. Unitarian) deprived me of any direct benefit from my maternal grandfather's substantial estate.
If 1,000 users contributed an average of $100, I assume that would be useful. I am sure 10,000 would be.
My original question remains. ( I like a tax deduction, but it is not essential.)