I believe most people go with their non dominant if they are only getting one implant. I got my xEM in my right hand despite being right handed because I plan to get an xM1 eventually and it is larger than the xEM. I wanted the larger of the two to be in my non dominant hand.
I’m awkward. Both parents are left handed but I went to a catholic daycare when I was a kid and they literally beat it out of me so I am mainly right handed for most things, but can learn most things with the left if I put time into it.
I got the NExT specifically to replace an access key fob, and most/all of the scanners for this particular system are on the left side so I put it in my L4. It happens to be my offhand, but more convenient for use.