Good news. So, I ended up ordering this part instead:
2227640-1 TE Connectivity / AMP | Mouser
As I needed a few other things and mouser had them in stock. The part arrived today, and I removed the broken connector:
I decided not to use the right angle connector because it would not have worked well in the chassis. The new connector by TE Connectivity/AMP looks more robust than the original as the area around the latch is thicker than the original. The original however, had gold plated pins, while the AMP connector had silver colored pins.
Removal of the original connector involved removing 3 screws from the backside, and slowly prying and pulling it out as straight as possible. Once I could get the flat edge of a thin screw driver in the middle, the rest was pretty easy to get it out the rest of the way.
Installation of the new connector was more challenging. It takes a lot of pressure to press the new connector in. I first made sure all the pins aligned correctly with the holes. Then I placed a thick piece of leather I had laying around underneath the motherboard as backing to push on, and pressed down on the connector with my thumbs, but it did not go in all the way. it did go in enough that it was holding on to the board; you could hold the connector and pull up and the board would come up with it. I then got the head of a plastic dead blow hammer and used that to press down on the connector with the weight of my body; i had to lean in a few times to finally get the connector seated in. Then attached the 3 screws from the back of the board.
After that, I installed the board into a chassis with SFF-8643 connectors to test it out and fortunately, everything worked! Created a few test zpools, generated some data, ran a few scrubs, exported/imported, scrub a few more times, etc. worked without any issues.
Now, if only I can find v3/v4 CPUs and DDR4 cheaply, I might actually have some use for this motherboard....