I may have had similar issue as OP. For me the CPU usage of Eddie-UI.exe was in range od 0.5%-3% constantly (even when Eddie was hidden in the tray).
Since Eddie is open-source and I'm a .NET engineer (I troubleshot a lot of app performance problems at work) I sat one Saturday afternoon and found that the issue was in the method call that gets network interfaces from system.
The fix is a couple lines of code - store NetworkInterface objects in process memory (monitor for changes) and call GetIPv4Statistics() on them instead if creating new ones every time.
I'm running with this custom Eddie build for over a year now without observing regressions and the CPU usage is stable at 0.0-0.1% in background After seeing this topic I re-tested with and without the patch on version 2.24.2. The results are visible on the screenshots. @Staff Feel free to test this patch [git apply file.patch] I'm using Windows - haven't tested other platforms
BR
network-interface-get-improvement.patch