Broken AC drain fitting

Make a plastic plate with spigot to glue into place.

Once repaired avoid repeating the action that broke the original.

I think what Solar Mike is stating in his answer is spot on ... however, the devil is in the details.

You need to create a new drain tube. Part of it will have the nipple which would attach to the tube. The other part would need to be a flat washer of some type, something you'd attach the nipple to. This washer portion would be about the same size the inner portion of what you are showing in picture one. You want it to fit up in there. You'll need to clean out the broken part within the circular portion, making it as flat as possible. Once all is ready, take some waterproof 2-part epoxy and affix the flat washer portion up where the hole in the evaporator housing, making sure the condensed water has a clear path to run out. You'll also want to put the epoxy into any cracks which may be there. The epoxy serves two purposes, first to affix the new nipple, and secondly to seal anything up. Once all is set and completely cured, re-attach the drain hose to it. Should work as good as it did new.

If you have a 3d printer, you could easily make the part you need.

I would put a rubber pipe onto one of these, then support the large end of this connector in place against the hole. You may even be able to file the hole to the correct shape so that this connector just screws in slightly-

Then put plenty of this stuff around it to seal it in place -

This sealant should stick well to both surfaces and won’t drip off like most glues will.

If it leaks once hard due to leaving a gap somewhere, just add more sealant over it.

Use Tiger Seal, not some random silicone.

You may even be able to get away with just holding the open end of a pipe in place against the hole and using the Tiger seal to glue it in place, then not needing the connector. Either way, you don’t want the pipe to go inside the casing which would mean that the water would have to rise above the pipe to drain out, keep the pipe or fitting flush to the casing.