I've been having a problem with searchpartyd for the past 3-4 years across multiple Macbooks (work and personal). Pretty much every Macbook I've signed into iCloud with has had the searchpartyd issue. Disabling bluetooth and force stopping the searchpartyd process worked for me to stop it, but not having bluetooth is pretty annoying. Nothing else suggested across many community threads solved the problem, but since it was happening across multiple Macbooks, it definitely seemed account / iCloud related. My particular issue would always start out using 100% of a CPU core, and every couple of minutes, it would start consuming another CPU core, until my entire CPU was being occupied by searchpartyd.
I was actually able to finally solve it for good last week though. For me, I had some 3rd party Airtags. I can see them in Find My if I go to the Items tab. These ones have a manufacturer "ACCUTag", firmware version "1.7.30". I got them several years ago. One of the tags was out of batteries for years and just showed up as unknown or not seen, I don't quite remember. I figured I would try to remove the tag from my Find My. I wasn't actually able to remove it from my Macbook, and had to go to Find My on my iPhone, find the dead 3rd party Airtag, attempt to remove it multiple times (the first couple of times just loaded forever). Eventually it disappeared from my iPhone, and after rebooting my Macbook, it also disappeared from Find My. And best of all, searchpartyd did not consume tons of CPU anymore. So I suspect there is a bug in Find My on Macs if it is a thirdparty Bluetooth tag and the tag goes missing or runs out of batteries. Annoying though since the issue has persisted across at least 3 MacOS major versions to my recollection.
