Is it appropriate to acknowledge Satoshi Nakamoto in a paper devoted to blockchain?

Why don't you just cite their original bitcoin paper in your introduction? I don't know the history of your field but if that was really a fundamental result it seems completely reasonable to cite it. Whether the author is anonymous or not doesn't change that.

According to google scholar the paper has over 7000 citations so you would have lots of company.

In general I would say a citation that acknowledges the importance of the work is a much stronger form of thanks than a mention in the acknowledgements section.

I think it would be appropriate to thank him in a thesis, but not in a paper.

There is a big cultural difference in how acknowledgments are used in theses and papers. In the common use (at least in my field, but I think this is general), acknowledgments in a paper are reserved for:

• people that actually helped on the topic of the paper, via direct personal interaction, for instance "We thank X for useful discussions" or "We thank Y for providing us the reference [5] and an alternative proof of Theorem 5"
• funding agencies
• host institutions for a visit, such as "This research was conducted when the first author was on a sabbatical leave at the University of W; she thanks UW for its support".

Other acknowledgments (such as general help, emotional support, parents and partners, etc.) would definitely look out of place. You can put these in your thesis, but in a paper you'd better stick to business and keep it as brief as possible. The acknowledgments section of a paper is not intended as a soapbox (unlike that of a thesis). There are exceptions, but they will raise eyebrows.

No one acknowledge any scientist leading/having led to a field with no direct interaction on the paper. So no.

I would find it inappropriate even in a thesis. You have other sections to highlight the importance and merits of someone, and you do so in a scientific and pertinent way, by referencing his/her work, for instance.