Note 20 5G (not ultra): Flex cable related to SIM issues?

(N981U) One end of the “thin” flex cable connects on the main board, and the other end connects down towards the bottom of the phone (the end with the charging part). Since this is a 5G version, the cable is actually a "T" cable, with a connection over to the 5G antenna on the side of the device (below the volume and power buttons). Here's the questions:
(1) besides the 5G, what does this cable do? If the cable is removed from the phone, what won't work?
(2) if the cable is connected top and bottom, but not on the 5G end, will it cause any problems besides 5G not working?
(3) Can this cable cause SIM issues?

Why am i asking? because while changing the battery i wrecked this cable in two ways: (a) mangled the 5G connector while taking things apart, and (b) mangled the cable connector on the main board end while putting things back together. I can change out the cable, no problem, except what's worse is I'm pretty sure I (c) hosed the main board connector as well. So, I'm running the phone without this cable at the moment, and USB charging isn't working, which might make sense (but it’s charging wirelessly, so this is fine for now). the *real* problem is that I'm having SIM issues. trying to figure out if SIM issues make sense for this cable, or if there's something else wrong I need to find?