Not that it matters, but I think KDE Connect was available even before Apple's cross device copy paste
The beauty of apples continuity feature is that the sync happens locally over Bluetooth/WiFi and secured by the Apple ID. Nothing is sent to a remote server, and each entry has a TTL.
I have 2 macs for work. One for my employer, and one sent by the company I am contracted to work for.
Contract-mac is hugely locked down, requires all traffic to go through the VPN, and only allows non-VPN connections to the VPN.
Work-mac is fairly ordinary, not locked down except for anti-virus.
To get Magnet and a couple of other Apple store apps on the contract-mac, I signed in to the Apple store. Immediately, copy and paste started working across both macs. I'm not sure of the mechanism by which the clipboard was being "shared", but it felt like I'd get chewed out by contract-mac's security folks if I continued using it.
It's convenient, for sure, but could very easily be against security policy in larger enterprises.
Source: Apple support to me when it stopped working
https://support.apple.com/guide/mac-help/copy-and-paste-betw...
“To use Universal Clipboard, your devices must meet Continuity system requirements. They must also have Wi-Fi, Bluetooth, and Handoff turned on in System Preferences (on your Mac) and in Settings (on your iOS and iPadOS devices). You must be signed in with the same Apple ID on all your devices”
System requirements more or less means “hardware is new enough” (https://support.apple.com/en-us/HT204689; I think the technical reason is that it requires a specific Bluetooth version and macOS/iOS version)
Apple doesn’t say it, but I think the devices also must be on the same WiFi network and within Bluetooth range of each other.
Edit: as a consequence, if you lend your iPad to somebody for a few minutes while working on stuff you don’t want them to know about, log out of your Apple account. Without it, they can paste whatever happens to be on your clipboard.
Conversely, if you borrow someone else’s phone, don’t copy any secrets to the clipboard, even if you later replace that by something innocuous.
it's automatic.