forcing square app icon
Your app's icon will be rounded when a launcher decides to make it rounded.
The "launcher" is just another app, like yours, but it is not your app - it is separated completely from it, and you can't normally influence any process that is separated from your app's process, OS will forbid that. Only sometimes you would be able to do something like that by utilizing some form of Inter Process Communication (IPC) offered by your OS, assuming of course that the process you want to communicate with is also 'willing to talk' with you [utilizes the same form of IPC to allow other process to change some of its behaviors].
Also the purpose of the Android Studio's wizard you used was to help you generate ready-to-use drawable files and it was just to save your time on making these drawables all by yourself in some image editor.
Any drawable set inside XML manifest file for being your app's round icon will be rounded a t the end and that is no matter how it actually looks. I don't think you can expect any currently available major launcher application to display some apps' icons as round and some as square. It would significantly harm its user experience.
I'm afraid you will have to adapt to this situation and make your square app's logo a little bit smaller and leave some empty space around it to allow end user's launcher app to draw a circle around this logo.
Here you can find official recommendations for designing Android apps' launcher icons: https://material.io/guidelines/style/icons.html#icons-icons-for-android and here you can read about the most current approach in a subject of Android apps' icons: Adaptive ones. Any other type of icon can be treated as 'legacy' and used only for compatability reasons when targeting APIs below 26.
Edit: In the comments section OP mentioned some apps that do currently have square icons in their newest versions and that turned out to actually be a small UX design flaw of its developers.
Just as an example, I've downloaded Bytecoin app OP mentioned, and this is how it looks like on my phone, Android 7.0:
The red object in the corner has ben cut off. I think we can assume that every other app on the Google Play that displays there with square logo [which looks good in their store pages because Google Play allows square logos] will look bad when installed on phones with modern versions of launchers, especially api >=26.
If your target SDK is 26 and android device version is 8, the app icon will be round.
One of the ways to achieve this is (Not sure if it is the right/best way to do it)
In AndroidManifest.xml I had to set
android:targetSdkVersion=“20”
<uses-sdk android:minSdkVersion=“16" android:targetSdkVersion=“20” />
android:roundIcon=“@mipmap/ic_launcher_round”
<application android:hardwareAccelerated=“true” android:icon=“@mipmap/ic_launcher” android:label=“@string/app_name” android:roundIcon=“@mipmap/ic_launcher_round” android:supportsRtl=“true”>
Ensure the ic_launcher_round images are Squared one.
I used the android studio to generate adaptive and legacy icons…
I deleted the ic_launcher_round images generated by the android studio.
I copied ic_launcher images(Generally the Square icons) to ic_launcher_round.
Now my ic_launcher_round is Squared icons.
(ic_launcher_round.png, ic_launcher.png, icon.png) all of them are the same images
After making this changes, rebuild the app. Now you should see Square icon when you install the app.