It's specifically the definition of "match_case" in the AST that is affected:

match_case = (pattern pattern, expr? guard, stmt* body)

    pattern = MatchAlways
         | MatchValue(expr value)
         | MatchConstant(constant value)
         | MatchSequence(pattern* patterns)
         | MatchMapping(expr* keys, pattern* patterns)
         | MatchClass(expr cls, pattern* patterns, identifier* extra_attrs, pattern* extra_patterns)

         | MatchRestOfSequence(identifier? target)
         -- A NULL entry in the MatchMapping key list handles capturing extra mapping keys

         | MatchAs(pattern? pattern, identifier target)
         | MatchOr(pattern* patterns)
          attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

Relative to the PEP 642 AST, the notion of a "matchop" is gone - MatchValue always compares by equality, and there's a MatchConstant node for the identity comparisons against None, True, and False.

The grammar, code generator, AST validator, and unparser are then updated to produce or consume the new AST nodes.