What about SQLite JSONB? Does it maintain order?

UPDATE: I think SQLite JSONB does maintain order. For example:

    select json(jsonb('{"a": 1, "b": 2, "c": 3, "d": 4}'));"
    -- {"a":1,"b":2,"c":3,"d":4}

And it does maintain order when adding new keys:

    select json(jsonb_insert(jsonb('{"a": 1, "b": 2, "c": 3, "d": 4}'), '$.e', 99));
    -- {"a":1,"b":2,"c":3,"d":4,"e":99}

(tested on https://codapi.org/sqlite/)