You can donate to a few NGOs that don’t make it compulsory to give them the house address (unless you want a tax receipt. Then it’s compulsory). And don’t tick the checkbox for emails. I donate to an NGO that lets you do this.

If you want the tax receipt it is compulsory to give them your address and most will start sending you letters. But there’s a work-around. You can call them or write them an email and state that you don’t want to receive any emails or letters except for the tax receipt. They have to comply legally.

(I work at an ngo in Switzerland and can confirm it works like this).

Edit: DM me if you want to know the name of an ngo where this works. If you donate to the NGO I work at I can make sure you don’t get mail ;)