Problema ao rodar "flutter run"

Já procurei na internet, mas não achei nada, sempre que uso "flutter run" ele diz o seguinte:

Unable to locate a development device; please run 'flutter doctor' for information about installing additional components.

mas quando eu uso "flutter devices" ele acha o meu smartphone conectado, ele está funcionando normalmente com o adb, consigo instalar apks e fazer outras coisas sem problema, quando eu escrevo "flutter doctor" ele diz:

[✓] Flutter (Channel stable, v1.17.5, on Linux, locale pt_BR.UTF-8)
    • Flutter version 1.17.5 at /home/luke/snap/flutter/common/flutter
    • Framework revision 8af6b2f038 (10 days ago), 2020-06-30 12:53:55 -0700
    • Engine revision ee76268252
    • Dart version 2.8.4

[!] Android toolchain - develop for Android devices
    • Android SDK at /usr/lib/android-sdk
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/docs/get-started/install/linux#android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, set ANDROID_HOME to that location.
      You may also want to add it to your PATH environment variable.

    ✗ No valid Android SDK platforms found in /usr/lib/android-sdk/platforms. Directory was empty.
    • Try re-installing or updating your Android SDK,
      visit https://flutter.dev/docs/get-started/install/linux#android-setup for detailed instructions.

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/linux#android-setup for detailed instructions).

[✓] VS Code (version 1.47.0)
    • VS Code at /usr/share/code
    • Flutter extension version 3.12.2

[✓] Connected device (1 available)
    • POCO F1 • 246c5306 • android-arm64 • Android 10 (API 29)

! Doctor found issues in 2 categories.

e quando eu tento usar o emulador ele diz:

Unable to find any emulator sources. Please ensure you have some
Android AVD images available.

alguém pode me ajudar por favor? Eu quero muito aprender flutter, estou usando Linux, na distro Lubuntu