TLDR: No, VAT should not be charged on digital assets received as a reward for mining, as there is no direct link between the consideration and an individualised service.
Answer
The remuneration in cryptocurrencies received by the miner is random in nature. It is not possible to identify an individualised service performed by the miner for a specific beneficiary. In the absence of a direct link between the consideration and the mining activity, the latter does not fall within the scope of VAT. Therefore, the miner is not required to collect tax on the digital assets received as a reward.