- Install ADB (Android Debug Bridge) on your PC; this walkthrough might help https://www.xda-developers.com/install-adb-windows-macos-linux/
- Download the Daydream SLR apk file from the SLR page
- Start your Mirage Solo and go to the Settings >> System >> About Phone
Activate the Developer settings by tapping 7 times on the Build number. Return to the previous screen to find Developer options near the bottom
- Activate USB debugging in the developer options
- Now connect the Mirage Solo via USB to your PC and accept the USB debugging question in the headset
- Install the SLR app via ADB command "adb install SLRDaydream.apk"
- After successful installation I rebooted to Mirage Solo
Now you should see the SLR app in the library. If you can't see it then you might have an older version of the SLR app. Then you have to go to Settings >> Daydream >> Developer options and activate "Show 2D apps in library". After that you can switch between 3D and 2D apps with a small icon in the library overview. If you start SLR that way then the app will be updated and it will show normally in the 3D library.
Thanks goes to Reddit user Elazar_DE who posted this walkthrough on https://www.reddit.com/r/daydream/comments/9g044p/how_to_get_slr_app_running_on_mirage_solo/