Let me please add the following:
To check for canons of specified composers (if they composed some and entitled them as "canon" in a way), we can do this (and other things which are interesting, IMHO) on Klassika.
Example:
https://www.klassika.info/Komponisten/Schubert/wv_gattung.html#Kanon __
Furthermore, I found this one, which has to be bought somewhere:
It says it contains "suggestions for practising", too, but it's unclear

whether these suggestions refer rather to exactly structural elements of the "canon" itself, than more to pianistic problems and topics.
Maybe some of you have it and can say more about it?
Kanon d-Moll für Klavier (1883) / Skrjabin. Mit Vorschlägen zum Üben von Frank Seifert ( =
in English: Canon d-minor for piano (1883) / Scriabin. Including suggestions for practising by Frank Seifert. )
Skrjabin, Aleksandr N. [Komponist]; Seifert, Frank [Bearb.] [Beteiligt]
Bad Salzschlirf : Antoni-Verlag [2001]
[3] pages. ; 30 cm
__
This guy seemingly has coped with some aspects of the topic "canon", too, on his site, but i didn't (and won't) check it out in detail:
https://sebastianweber.de/blog/2011/12/14/groove-training-8-kanons/__
People who are scientifically interested in the area of canons could be interested in this congress-paper:
Canons and canonic techniques, 14th - 16th century: theory, practice, and reception history : proceedings of the international conference, Leuven, 4 - 6 October 2005 / ed. by Katelijne Schiltz and Bonnie J. Blackburn
Schiltz, Katelijne *1974-* Identity ; Blackburn, Bonnie J.
International conference ; (Leuven) : 2005.10.04-06
Leuven [u.a.] : Peeters, 2007
XXVIII, 498 S. : Ill., Notenbeisp. ( = examples of notes/scores)
Analysis in context : Leuven studies in musicology ; ZDB-ID: 25316011 ; 1
ISBN: 90-429-1681-8, 978-90-429-1681-4
Greetings from: 8_octaves!
