Android Oreo 8.0 - Workarounds, Android-system notification removal, Gmail label custom sound notification replacement

An upgrade from Android Nougat 7.0 to Android Oreo 8.0 gave nothing but problems.

Here is the result of fails and if possible, how to address them.

- Sounds. Beware that ringtones and notification sounds are being resetted when upgrading, maybe it only affects sounds stored on external SD cards.

- Notifications play over each other. This is probably due to the "channel"/"category" system for notifications and it causes notification sounds to run over each other. Instead of playing one sound for mail I now get many.

- Gmail, custom sounds for labels can no longer be assigned.
A discussion is available at: https://productforums.google.com/forum/#!topic/phone-by-google/xTXRdcp7yIM and a workaround is to install an app that listens to the keywords of incoming notifications and plays a custom sound, for example Message Notifier Pro ( https://play.google.com/store/apps/details?id=jp.co.minds_net.msgnotifypro&rdid=jp.co.minds_net.msgnotifypro ).

- Brightness sensor is too sensitive and adjusts to much. The display is too dark in dark situations.

- Android system notification about apps running in the background is constantly displayed. It cannot be cleared and is quite annoying. A workaround is to install AutoNotification ( https://play.google.com/store/apps/details?id=com.joaomgcd.autonotification ), create a 
regex filter and set it to hide all notifications matching the text in the notification.