Donation Page

click settings>general and untick the startup page.

On Thunderbird. Getting the begging page almost every day. becoming annoying. I wouldn't mind if I were a freeloader but I already donated.

If you are seeing https://start.thunderbird.net/ it is the start page whose primary purpose is not donation, and has no capability to know that you have donated. But as has been mentioned it can changed. Documentation at https://support.mozilla.org/en-US/kb/how-disable-or-change-thunderbird-start-page.