@FediThing @feditips most probably you need to look into OSS https://vat-one-stop-shop.ec.europa.eu/index_en and have a talk with your local state revenue service. For example, in my country SRS has an option that a person signs up to pay VAT and pay OSS through them, then you do not need to sign up for OSS in other countries.
I do not know all the details, but that's what I have gathered from local SRS.
@mariilasa
That only covers sales of goods or services though? I am not selling any goods or services.
I'm doing the services and sites for free (in fact I'm having to pay money to host the sites), and people can send a donation if they want to. There is no transaction going on as such.