I feel quite repulsed by the fact that the first thing you see when opening the post is a huge donation card.

I used to feel that way about prominent banners / cards. Then I tried to get donations on my own site and until I became hyper-aggressive I never received even a dollar. It was frankly disheartening. Now, it is not yet sustainable but at least moving in the right direction. In other words, they really have no choice.

How much do you donate?

I want to see KDE still improving and keeping up in another 30 years. To me it's no different from a telethon for PBS or a poster for Friends of the Library. Intrusive? From a certain point of view, but it pays the bills.