How to bypass system /signature level for a modified system apk? I made a modification on a system app but it should be signed with the same certificate as the Firmware to work properly, is there any workaround to bypass this ?
As far I know you need a custom firmware to do it (I guess you don't have access to the firmware keys to resign your apk) so:


a) You can modify,  compile and install your custom Android that skips the signing verification in apps that request to use the android.uid.system user or
b) You can install a custom ROM signed with AOSP keys (most of the custom ROMs are signed using the testkeys from AOSP) and sign you app using the same key in order to get the system level (you can use  keytool-importkeypair tool to create a keystore and used it on Android Studio or gradle