as you know, measurement protocol in GA4 is very limited. i have problem with tracking events from mobile devices in measurement protocol - at my reports there is only 'desktop'. I saw many suggestions of solution this problem (like using custom definitions) but it it looks inappropriate. If you had same problem at your project and solve it please give me know.
also I found this answer from Google Analytics API team but there is also no solution
I found a solution of this problem. I added some custom parameters on measurement protocol request, checked it at 'Event builder' by Google and then added some custom parameters by 'event' on GA4.