If argument_list node type or argument node type is set to always-indent, the block opener would always be indented, as well.
This pull adds align-to-node-line, a group that allows to set a list of node types that the current node will try to align to its indentation, instead of following its parent indentation. The above example has the following configuration to work (ommiting the other indentation rules, I'm only focusing on the relevant ones):
(indent-all . ;; these nodes are always indented
(align-to-node-line . ;; these nodes are aligned to the first column of the
;; line where the first node contained in the list is found.
((block . (lambda_expression)))))
So, instead of the block inheriting the indentation of argument_list it tries to find an ancestor with type lambda_expression, finding one, it indents to its line's first column. If no lambda_expression is found, the other rules follows as normal.