Links:
Here are some links, both for fan and official pages on Ankh, as well as some things related to OOO more generally.
Official:
Kamen Rider Zukan Pages:
🔗(Archived) TV Asahi's Page on Ankh
Fan Links:
🔗Ryosuke Miura Fansite: While this is focused on Ankh's actor Ryosuke Miura, you can find various links and information on his work for OOO. There are dedicated pages to Hesiei Generations Final and OOO 10th too. It's a great information repository and has links to various articles and more.
Other than one site that there is not much I have found yet. I am actively trying to find fansites, either ones archived or still up but have had horrible luck. Such is the pain of getting into a show over a decade since it aired.
If you're looking for Fanwork recs, those would be in the Fanworks section instead of being listed here.
I'm sure I'll find something eventually, so check back!