When I click donate I eventually wind up at the Select Currency section of the Donate page. Clicking USD (top entry) immediately takes me to paypal with a donation value of zero. I never get a chance to select the amount. Same result in Fedora-38/Gnome/Wayland/Firefox, Win10/firefox-portable, and Win10/Edge. At that point I just click cancel. Maybe I'll check back in a month or two and see if the behavior is more normal.
Maybe you're using some special Paypal API and I'd have been able to select the amount after clicking confirm. I've never been able to adjust the amount from "inside" paypal with any other site. I suspect many people are paranoid like me when it comes to internet financial transactions. I cancel out of anything that looks the tiniest bit unusual.
Doesn't look like I can attach a screenshot.
Edit: link to screenshot payzero.png (180KB)
That's what the PayPal UI looks like. Click on the 0 and type whatever number you'd like.
Sometimes, the impossible can become possible, if you're awesome!
Oh. Duh. (Thank you.)