Yes I understand that but if you can accept donations, you can surely hack together a quote and state that the payment will go through your donation platform. In most country I believe you don't have anything to do at all bellow a certain threshold.
It's just a matter of not offering to work for free to a corporation that really doesn't need your generosity.
And sometimes a side project doesn't want to be a side hustle; dealing with payments and tax implications is time not being spent on the core project. It's an individual choice as to whether the time cost of accepting payment is worth it.
It's just a matter of not offering to work for free to a corporation that really doesn't need your generosity.