Dear Future Self whenever you start an android dev project

I noticed every time I do Android development. I mean every time!
Just every time! It always happens! I can't connect my phone to develop, so here! Don't ever forget this!

This was copy and pasted from a post I did in an VR group. This was meant for Unity, but maybe it would work with Android Studio, too.

[SOLVED] Problem: I'm having trouble with Unity to recognize the S7 when I do a build and run. When I run 'adb devices' in cmd, it gives me an empty list. I'm on Windows 10.

Solution: I switched USB cables. Updated my drivers from device manager.

Anyone know how I can get Unity to build my app to the S7?
#olpquestion

Things I already tried:
1. Since downloading just the command line android zip didn't work, I downloaded the whole Android Studio for the adb, and it still listed empty.
2. Phone is in developer mode with USB debugging in MTP.
3. Downloaded an app, "USB Driver for Android", for developers who have the same problem and "magically" have adb recognize their phone. But didn't work.
4. adb kill-server and restart. plug and unplug usb. restart computer. check the system info on my pc hardware and the pc recognized it as a mass storage
5. downloaded usb driver on official samsung website but it still didn't recognize Android Phone has been plugged in when I look at the device manager even with the view showing all hidden devices. It recognizes as a USB root hub. so this might be a problem?

Any suggestions are appreciated. This is taking me like 5 hours to figure out. And I read a few comments from people who said it took them 2 days. o_o;;