I wouldn't bet on "most likely you wouldn’t be considered tax resident anywhere" - first, you have a default tax residency at your country of origin and the loc

I wouldn't bet on "most likely you wouldn’t be considered tax resident anywhere" - first, you have a default tax residency at your country of origin and the local law is likely to say that you lose it only if you can prove another tax residency. Second, countries are likely to err on the side of caution which benefits them, so if you have unusual arrangements, then it's quite plausible that you are a tax resident of multiple countries and owe taxes to all of them - many countries have bilateral treaties to avoid dual taxation (which is the default outcome in many cases), so a digital nomad in an unusual situation might owe taxes to two or more countries, but are very unlikely to owe tax to no country. "the burden of proof would be on the tax authority" - no, definitely not. The tax laws generally assert their claim on all income accrued in a certain country. The abovementioned 'non-dual-taxation' treaties have a process so that in reasonable scenarios the worker only pays tax in their home country, but if they don't apply (for example, because the 'home country' is a tax haven with whom there such a treaty isn't made), they owe tax where they earned the income. The mere fact that you are a tax resident somewhere else does not mean that you're exempt from local taxes, that requires fulfilling the criteria of those dual taxation treaties. The weak point there is enforcement - there are all kinds of ways how a digital nomad can ensure that they won't be hassled much to collect the taxes they owe and they often can avoid paying them - but legally, they still owe them and are at the mercy of the authorities not finding out or not caring.