How to digitally sign an android apk file?

Question

Google Play

Google Play only accepts applications signed with a key.
I have had a problem for more than a week now that I created the apk file, but I cannot sign it with a certificate.
Tell me how to generate a project with a key, so that Google Play would accept it?
The project was originally on Ionic, but as I understand it, both Flutter and React Native have a similar story. I can't publish any of the frameworks on Google Play.

I tried like here https://ionicframework.com/docs/deployment/play-store

keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000

jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore HelloWorld-release-unsigned.apk alias_name

But I am getting errors.
By the way, Android Studio does not build the project with the key either.
I don't know what could be wrong?