@ced, The post where you mention the number of hours spent by B2CK (excl. personal time) encourages donating for me, however it is not very explicit, especially on the donation page.
For me fund-raising campaigns, for ex. OpenBSD fund-raising campaign 2020, or the Wikipedia fund-raising campaigns motivate donating.
These (sometimes) contain two pieces of info: The target (how much money is needed in order to carry out the annual plan) and what will be done with this money(the annual plan): for ex. x EUR electricity+internet for own servers, x EUR VPS, x hours of work-time, etc. Also perhaps mention for example that if half of the users donate x EUR then the goal will be met.
Frankly the amounts donated on the donation page are disappointing.
Perhaps have a modest goal for 2021, and increase it based on the success (or lack of) for 2022.