Is there a single Linux phone/tablet that can last an 8 hour day of actual use? Librem/Pinephone/Juno can't. My uConsole can't. Different category, but my MNT mini laptop lasts like 4 hours and can't be left in standby for too long or it drains to zero.
Meanwhile, it's been 10+ years since I've worried about daily battery life on mainstream mobile devices, even my 3-5 year old ones. I can fall asleep with Youtube playing and it's still playing when I wake up. I'm certainly not here to dunk on Linux phones. I want one! But if someone willing to put forth above average effort to use these devices can't realistically daily drive them, who can?
Hell, my watch runs Tizen and that's running a bog standard Wayland + PulseAudio + systemd setup: https://docs.tizen.org/platform/porting/system/#systemd
With the right kernel drivers, configuration, and tweaks, with a well-configured userland on top of that, you can run the "normal" Linux stack in a mobile device.
Getting applications to conform with an API that won't let them drain the battery in the background to make sure notifications don't arrive two seconds too late is much harder. Desktop applications don't really like being suspended/resumed the way mobile applications do.
Are there well-known good practices?... Or, do they need to be rediscovered as they are perhaps proprietary know-how?