Thank you Andre!
In order to get Poweramp and the Unlocker to show up I had to uninstall both and install both again.
Now, they both appear and I can set them to NEVER SLEEPING APPS.
However, there is still the issue of Poweramp not playing continuously 24/7. It randomly stops. The EQ also randomly disable itself.
May you please provide a solution for that?
For others coming to here from Google. Here is some information on our experience streaming audio 24/7 for a business or whatever purpose for ambience music.
We also experimented with streaming through Bluetooth to our speakers. These were our results:
Battery drains MUCH FASTER. We have a smart switch that turns on every 4 hours to charge all 6 of our phones total for 10 minutes. Using Google Cast, the battery drains so little that the phones will eventually top off to 100%. However, streaming using Bluetooth causes the phones to eventually go to 0% battery.
The audio quality is much better through Google Cast.
We use Samsung A32 and LG Stylo 6 phones.
We used BlackPlayer and Poweramp. Poweramp has much better EQ features. However, BlackPlayer does not randomly stop playing. It will play 24/7 forever until the user stops it - WHICH IS WONDERFUL!!! However, Black Player does not support Google Cast.
Ideally, we would love to get Poweramp working 24/7.
This is a completely unrelated topic = We implemented a smart switch controlling a power strip with all of the USB power adapters for interval charging. This is totally not necessary but I am trying to preserve the batteries of these phones. Ideally, I want them to drain to about 60% and then charge to about 70% using interval charging. This keeps the batteries in the ideal capacity range and there's very little risk of overcharging or fire. I don't know if keeping a phone plugged and charging 24/7/365 is a fire risk but this was easy to implement.