The connections under my sink have a flexible tube that I’d like to replace with rigid tube. The stub out from the wall doesn’t have the nut and threaded connection I’ve seen before, and they’ve used what I think is called a no-hub connector.

Would I use the no-hub connector on the rigid tube or do I sweat something like this on? https://www.brasscraft.com/product/1-12-in-o-d-tube-x-1-12-in-fip-3/ Or is there some other way?

I’ve soldered the narrower water supply lines, but nothing this large. Is there anything to consider other than heating it longer?

The stub out has corroded on the bottom and there’s a thin crack that the no-hub fitting covers, so there isn’t a leak now, but I don’t know if that will be covered if I sweat on a connector. Is there a way to deal with that crack?

As some extra info, I think that some stubs are threaded into the vertical pipe. This isn’t threaded in and doesn’t look like it can be removed without opening the wall and replacing it.