The tutorial shows long inserters 2 being researched which allowed inserters to pick up and drop off items 3 tiles away. However, I can't find this research. Was this research removed at some point?

Just realized in mod settings there's a check box to enable long inserters 2 research and more inserters 2 research. After checking these boxes, the research is back! Problem solved!

Yeah, it was requested that there be an option to turn it off, because some people thought it was overpowered.

it should be on by default.