Please Help Me Recover Island Data

My switch unfortunately broke recently and I bought a new one on Amazon in hopes of recovering my island, because I knew I had it backed up on my Nintendo online account. When I called support to recover it, they told me it couldn’t be done bc my new switch serial number indicates it’s from Japan, and my old switch with my island data is from the US. The representative told me if I borrowed a friend’s US switch, I could call back and recover my island data on that switch, then use the island transfer tool to transfer my island to my Japanese switch. Does anyone know how I do that, does that involve my friend to log out/unlink their nintendo online account on their switch? Would that cause any negative consequences to their own ACNH island or any other game save files?

Thanks anyone for your help.