How to start service 'package' with ADB

Using adb, I uninstalled some system apps on my device. Sadly, I uninstalled something important, and now the device is in a bootloop. During boot there is a window of time which I'm able to login with adb. But when I try to reinstall the system apps: adb shell cmd package install-existing --user 0 com.xyzname I get this error: Can't find service: package I used to be able to run install/uninstall commands in this bootup window, but now the service 'package' isn't being started. I tried looking up how to run services with adb, and I found [some commands using am](https://stackoverflow.com/questions/7415997/how-to-start-and-stop-android-service-from-a-adb-shell/18703083) , but nothing pertaining to specifically running 'package'. I need to get service 'package' to run. Begging for help here.