Mr. GMFumbled through sparse documentation on disparate sources before I found that there is a command to enable a license for the "_shell" command for my new-to-me Mellanox SX6036 switch. Once I had that figured out, I was able to follow along with several guides and get Ethernet enabled instead of the proprietary Infiniband thing. With all of this done, I've changed the default login and then started uploading newer firmware via the web UI.
I also ordered some cables and keystone jacks and stuff, totalling more than I spent on the switch... It's still going to be nice to have once it's all set up..!
Plus this way I'm forced to fix my old "oops I ordered multimode fiber instead of singlemode for the run to my office" mistake. When this is done, I can run both upstairs drops to a patch panel and a QSFP+ breakout to four spots on the same panel, then run (very) short patch cables to connect the drops to the breakout ports.