0xC0DED0D0
Note that it only requires USB Debugging temporarily to give the permission to the app within each profile, you can turn it right off again afterwards. It's more of a theoretical risk in my opinion. If you distrust the web tool to do it automatically for you, you can instead do it manually with the adb cli tool
I'll personally use the web tool. It is minimal, pure javascript, happens completely in the browser.
I'm pretty certain that a workaround for IPS default-applied by the GOS team will absolutely not happen. But I have hopes that at some point GOS just ships with a better native solution for this. Compared to 3rd party apps like Inter Profile Sharing, a System-level app would have many much cleaner ways to implement this.
Until then you have the choice to: Continue using Inter Profile Sharing with a one-time-setup-workaround via USB Debugging, use e2ee messengers with accounts for each profile, use e2ee cloud synchronization, use a USB-C stick, or use tools like KDE Connect or similar which use an active (W)Lan connection. (Let me know if I missed an option)
Theoretically there's still some side-channels left that would allow developing an app that exploits some other leftover loophole without requiring any system permission workaround. The Android 17 fix still has a side-channel for example: Binding a port in one profile blocks that port for other profiles. So you can basically communicate between profiles by binding ports. I considered that route for a moment because it sounded fun, but I went for the one that is more likely to be stable and fast instead^^