Unity Remote 5 is using HKEY_CURRENT_USER\Software\Unity Technologies\Unity Editor 5.x\AndroidSdkRoot_h2651068356. Instead, it should use the value from Unity Preferences > External Tools > SDK

Steps:
1. Install Unity via Hub and select the checkboxes for the built-in Android Build Support SDK/NDK/JDK
2. Install and open Unity Remote 5 on the Android Device (https://play.google.com/store/apps/details?id=com.unity3d.genericremote)
3. Connect the Android device via USB
4. Open CMD and enter
taskkill /f /im adb.exe
(if it doesn't work, then enter "adb kill-server")
5. Now enter
reg add "HKEY_CURRENT_USER\Software\Unity Technologies\Unity Editor 5.x" /f /v "AndroidSdkRoot_h2651068356" /t REG_BINARY /d 0
6. Create and open a New Project in Unity > Change Build Target to Android
7. In Menu bar: Edit > Project Settings > Device to use > Any android device
8. Click the Play button in the Editor

Expected: project appears on the device.
Actual: nothing happens - project does not appear on device.

Reproduced with: 2018.4.23f1, 2019.3.16f1, 2020.2.0a13

Reproduced with:
VLNQA00096, Samsung Galaxy S8 (SM-G950F), Android 8.0.0, CPU: Exynos 9 Octa 8895, GPU: Mali-G71
VLNQA00229, Oneplus OnePlus6T (ONEPLUS A6013), Android 9, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630
with
Windows 10

WORKAROUND:
Edit HKEY_CURRENT_USER\Software\Unity Technologies\Unity Editor 5.x registry and set AndroidSdkRoot_h2651068356 to the path of built-in SDK path.