Hey @leocg,
Thanks for the reference.
Additional research reveals the Opera Developers have worked on this in the past. Not sure they still are, especially with Opera One. Perhaps you can ping them to confirm.
Here's a great, short list of references they can use:
https://dev.opera.com/blog/wcag-2-0-3/
https://dev.opera.com/blog/opera-accessibility-where-we-re-at/
https://dev.opera.com/tags/accessibility/
https://stuff.mit.edu/afs/sipb/project/opera/share/help/access.htm
https://www.w3.org/WAI/standards-guidelines/wcag/
https://www.w3.org/WAI/standards-guidelines/wcag/#versions
It would be best if Opera One met WCAG 2.2 guidelines. They are scheduled to be released this year (2023).
Hope this helps a bit.
Cheers.