The Adobe CMap Resources GitHub repository is listed as a normative reference in section "2 Normative references" of ISO 32000-2.
Older versions of the PDF Reference contained in "Table 117 — Character collections for predefined CMaps, by PDF version" the information which supplement of each supported character collection belonged to a specific PDF version. With 32000-2 the content of this table was dropped, and it says now:
Table intentionally empty to retain table numbering in this document (2020). Information is now located in the appropriate normative reference for each character collection.
Here in the Adobe CMap Resources GitHub repository I could not find the information referred to by the text in Table 117 of ISO 32000-2.
I had raised this as pdf-association/pdf-issues#40 against the PDF Reference itself, and I was told by @petervwyatt that this should be handled in the Adobe CMap Resources GitHub repository README.md file.
For the purpose of being a normative reference of ISO 32000-2 this repository should contain the immutable information which character collection supplements belong to PDF 2.0 (and in the future for newer versions of the PDF standard as well).