A Turing machine is a universal computer: it can compute anything that any other computer can compute. A human being can specify a Turing machine and the data it's acting on and carry out the steps that the machine would execute. Human beings have also constructed computers with the same repertoire as a Turing machine, such as the computer on which I am writing this question. There are articles on Less Wrong about mind design space, such as this one:
https://www.lesswrong.com/posts/tnWRXkcDi5Tw9rzXw/the-design-space-of-minds-in-general
in which the author writes:
The main reason you could find yourself thinking that you know what a fully generic mind will (won't) do, is if you put yourself in that mind's shoes -
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If you read the quote carefully you will find that it is incompatible with the position you are attributing to Deutsch. For example, he writes about
which would hardly be necessary if computational universality was equivalent to universal explainer.