The example file in the wiki  (at https://wiki.contextgarden.net/PDF/A) no longer verifies as compliant PDF/A. VeraPDF rejects it, and https://www.pdf-online.com/osa/validate.aspx complains:


x107.pdf
Compliance pdfa-1b
Result Document does not conform to PDF/A.
Details

Validating file "x107.pdf" for conformance level pdfa-1b

Invalid content of XMP packet header attribute 'begin': '??'.

The property 'pdfx:ConTeXt.Support' is not defined in schema 'PDF/X ID Schema'.

The property 'pdfx:TeX.Support' is not defined in schema 'PDF/X ID Schema'.

The property 'pdfx:LuaTeX.Version' is not defined in schema 'PDF/X ID Schema'.

The property 'pdfx:LuaTeX.Functionality' is not defined in schema 'PDF/X ID Schema'.

The property 'pdfx:LuaTeX.LuaVersion' is not defined in schema 'PDF/X ID Schema'.

The property 'pdfx:LuaTeX.Platform' is not defined in schema 'PDF/X ID Schema'.

The document does not conform to the requested standard.

The document's meta data is either missing or inconsistent or corrupt.

The document does not conform to the PDF/A-1b standard.

Done.