IDo I need to unlock the bootloader first?
Then install TWRP?
Then flash the ROM?
Yes - exactly that. Use the TWRP linked to in the first post.
I have no problems with whatsapp on stock. The phone manager is a beast and you have to turn off so many settings to get things to work in the background. Have you tried ignore battery optimisations?
My (new) phone manager settings are:
Cleanup:
Settings / Automatic cleanup: Off
Whitelist: All items selected
Battery:
Close apps after screen lock: All deselected
Settings - Close excessively power-intensive apps: Off
Settings - Keep WLAN on during sleep: Always
Auto-launch:
All: Selected
Lock screen cleanup:
Close all: Off
In the normal Settings page:
Apps / Settings / Special Access / Ignore Optimisations
Change Allowed to All Apps
Change all required apps to Allow
I suspect the setting you suggested is the latter. I'll give this a go. If it works, i'll write it up formally, post it on my Blog and link to it from the first post.
The Chinese Huawei ROM is SO keen on killing things it's untrue!
Mike