A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
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One more, if you try aar plugin, you can open .aar file into a zip file and check out /libs/ folder If you have classes.jar file in your /libs/...
Although following the above, you got error, please check up your android app:graddle change below compile filetree(include:['*.jar'], dir:'libs')...