Anonymous artists have made money for years in all sorts of jurisdictions, it’s definitely possible to do. e.g. banksy, the residents, the rubber bandits, TISM
Yes, but these are true artists that make one-off sales. It is not a business for them(not legally). Where you have no legal obligation to become a "business". Author on Patreon on the other hand cannot claim to be "opportunistic" seller. They make repeated sales there, therefore it is taxable income and therefore they must become a legal entity of some sort and abide by the legal and tax laws of the consumer tax law in their country of origin.