With the largest crypto exchanges, it will hardly be possible to circumvent the proof of source of funds. However, it is permitted to buy or sell Bitcoin from private to private in a direct manner - i.e. without using an exchange. In most cases, you do not have to provide proof of source of funds to private buyers or sellers. However, we cannot advise this method. If you buy or sell Bitcoin "quasi anonymously", you will always lack important proof in the end. Sooner or later, this is likely to lead to disadvantages. However, if you attach great importance to owning cryptocurrencies as unmolested as possible, you can choose this path.