Help identifying a walkout door threshold and repair options
A quick update so the question can be closed. I ended up cutting out the old one and installing a new adjustable aluminum threshold from Home Depot. I had to saw open the hard black plastic and the aluminum ramp, breaking them into pieces. I also used an oscillating multi-tool to cut into the door jambs and scraped the old caulk around the perimeter. Finally I pried everything out. Installing was relatively easy. I just had to cut a few wood blocks to fill under the door jambs. With some cleaning, a fresh paint and caulk, the end result looks half-way decent: