First of all, thank you so much for your donations.

To turn off the popup, head to System Settings -> Notifications, search for "Donation Request" and turn it off.

Ahhh thanks!

I should have looked for it myself but every time it happened I was busy doing something else and then I forgot (yay ADHD).

And thanks to you for making KDE. I really don't like this time where computers are becoming more locked-in and opinionated (e.g. I can't configure it the way I want). KDE is a breath of fresh air. I have extensively reconfigured it and I haven't even needed to use a single plugin. So I've donated for years now because I really appreciate the work.

Even more specifically, the full menu chain is System Settings -> Notifications -> Application Settings, which then includes a search bar where you can enter "Donation" or "Request for Donation". (Mentioning it since entering that term in the main search bar doesn't bring up any results)