Android Design Support Library for API 28 (P) Not Working

Support library dependencies in Android Q

Support libraries will not be updated past 28. You need to migrate to androidx.

See support library documentation where it says:

Note: With the release of Android 9.0 (API level 28) there is a new version of the support library called AndroidX which is part of Jetpack. The AndroidX library contains the existing support library and also includes the latest Jetpack components.

You can continue to use the support library. Historical artifacts (those versioned 27 and earlier, and packaged as android.support.*) will remain available on Google Maven. However, all new library development will occur in the AndroidX library.

error crash implementation 'com.android.support:appcompat-v7:28.0.0'

How about migrating to AndroidX by selecting Refactor > Migrate to AndroidX and let the refactor do the work

It seems you don't want to migrate to AndroidX but you should give it a try, since android support 28.0.0 is the last release and android will only update androidx from now.

https://developer.android.com/topic/libraries/support-library/revisions#28-0-0

This is the stable release of Support Library 28.0.0 and is suitable for use in production. This will be the last feature release under the android.support packaging, and developers are encouraged to migrate to AndroidX.

What is the AndroidX equivalent of support-compat library?

That would be

implementation "androidx.core:core:1.3.2"

You can find a list of all the mapping to AndroidX at https://developer.android.com/jetpack/androidx/migrate/artifact-mappings

Can I use library that used android support with Androidx projects.

You can enable Jetifier on your project, which will basically exchange the Android Support Library dependencies in your project dependencies with AndroidX-ones. (e.g. Your Lottie dependencies will be changed from Support to AnroidX)

From the Android Studio Documentation (https://developer.android.com/studio/preview/features/):

The Android Gradle plugin provides the following global flags that you
can set in your gradle.properties file:

android.useAndroidX: When set to true, this flag indicates that you want to start using AndroidX from now on. If the flag is absent,
Android Studio behaves as if the flag were set to false.

android.enableJetifier: When set to true, this flag indicates that you want to have tool support (from the Android Gradle plugin) to
automatically convert existing third-party libraries as if they were
written for AndroidX. If the flag is absent, Android Studio behaves as
if the flag were set to false.

Precondition for Jetifier:

you have to use at least Android Studio 3.2

To enable jetifier, add those two lines to your gradle.properties file:

android.useAndroidX=true
android.enableJetifier=true

Finally, please check the release notes of AndroidX, because jetifier has still some problems with some libraries (e.g. Dagger Android): https://developer.android.com/topic/libraries/support-library/androidx-rn

Android Material and appcompat Manifest merger failed

Just change "rc01" in first and last line inside dependencies to "alpha1"
This is working for me