Like, can one keep the anonymity using a 3rd party wallet that can handle the amounts in all addresses and create transactions for my needs and still keep the anonymity?
Can't you do the same with a non-custodial wallet that supports coin selection? (Such as Electrum)
So, my dilema here is if I want to keep anonymity, I have to use a new address for every amount received/sent but to do this I need to trust a 3rd party app or code or service (in case of web sites).
There's no need to trust a third party app. You only need an HD wallet that derives new addresses each time it's queried.
Your text is a little bit confusing. In case I haven't understood it correctly, could you elaborate?
Yeah, I think I got a bit confused myself while I was typing the question!
If I understood, the OP is asking about the receivers of the donations, opposing to what I understood in the first place, from the thread title.
My question, without introducing any of my thoughts to keep it simple, is how receiving for instance, 10 different donations in 10 different addresses, keeps you in anonymity or how it protects your privacy... If I totally agree with the answer, then great, I got it, if not, I'll keep asking further questions until I get it.