Hello,
I'd like to mention a few nits about Knot's documentation, if you don't
mind. :)
1. Docs linked to from 
https://www.knot-dns.cz/documentation.html have
   URLs which don't look permanent; this makes it difficult to link to
   individual pages. It would be better imo, to have permanent URIs.
2. The usage message for [knotc flush] says "Flush journal and update
   zone files.". I understand this to mean zones that have received
   updates (RFC2136) will be written out, but this doesn't occur. I note
   zones are written out only at the end of a `zonefile-sync' period.
3. ixfr-from-differences, while documented in the manual, points to
   'Controlling running daemon', but it doesn't say there, that the
   syntax is 'on/off'.
   Enabling this in zones {} doesn't seem to do anything here: I was
   expecting to see a "*.ixfr" or some such file containing diffs, but I
   get none; neither for incoming xfr, nor for DNS updates.
4. Docs specify in 'Controlling running daemon' there is a knotc option
   -a, but the code doesn't have that: knotc: invalid option -- 'a'
   Same for 'Running Knot DNS' chapter.
Regards,
        -JP