I have this from your example....
Because no versions of firebase_core match >1.0.4 <2.0.0 and firebase_core 1.0.4 depends on firebase_core_platform_interface ^4.0.0, firebase_core ^1.0.4 requires firebase_core_platform_interface ^4.0.0.
And because no versions of firebase_core_platform_interface match >4.0.0 <5.0.0 and firebase_core_platform_interface 4.0.0 depends on plugin_platform_interface ^2.0.0, firebase_core ^1.0.4 requires plugin_platform_interface ^2.0.0.
And because path_provider >=1.6.4 <2.0.0-nullsafety depends on path_provider_platform_interface ^1.0.1 which depends on plugin_platform_interface ^1.0.1, firebase_core ^1.0.4 is incompatible with path_provider >=1.6.4 <2.0.0-nullsafety.
So, because flutter101 depends on both firebase_core ^1.0.4 and path_provider ^1.6.11, version solving failed.
I have this from your example....
Because no versions of firebase_core match >1.0.4 <2.0.0 and firebase_core 1.0.4 depends on firebase_core_platform_interface ^4.0.0, firebase_core ^1.0.4 requires firebase_core_platform_interface ^4.0.0.
And because no versions of firebase_core_platform_interface match >4.0.0 <5.0.0 and firebase_core_platform_interface 4.0.0 depends on plugin_platform_interface ^2.0.0, firebase_core ^1.0.4 requires plugin_platform_interface ^2.0.0.
And because path_provider >=1.6.4 <2.0.0-nullsafety depends on path_provider_platform_interface ^1.0.1 which depends on plugin_platform_interface ^1.0.1, firebase_core ^1.0.4 is incompatible with path_provider >=1.6.4 <2.0.0-nullsafety.
So, because flutter101 depends on both firebase_core ^1.0.4 and path_provider ^1.6.11, version solving failed.