Adjusting a mode function for the deprecation of anyarray

We have had and used this basic dumb useful aggregate in PG 13 and earlier:

CREATE OR REPLACE FUNCTION _final_mode(anyarray)
RETURNS anyelement AS
$BODY$
SELECT a
FROM unnest($1) a
GROUP BY 1
ORDER BY COUNT(1) DESC, 1
LIMIT 1;
$BODY$
LANGUAGE sql IMMUTABLE;

CREATE AGGREGATE mode(anyelement) (
SFUNC=array_append,
STYPE=anyarray,
FINALFUNC=_final_mode,
INITCOND='{}'
);

I can't seem to figure out how to adjust the mode(anyelement) bit now for
PG 14 and the loss of anyarray. Changing STYPE to anyelement yields
"function array_append(anyelement, anyelement) does not exist" and changing
it to anycompatiblearray yields:

ERROR: cannot determine transition data type
DETAIL: A result of type anycompatiblearray requires at least one input of
type anycompatible, anycompatiblearray, anycompatiblenonarray,
anycompatiblerange, or anycompatiblemultirange.

What's the obvious thing I am missing here? Thank you.

--
Wells Oliver
wells(dot)oliver(at)gmail(dot)com <wellsoliver(at)gmail(dot)com>