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?
I think UBPorts and Sailfish prove that Linux for phones is practical if you're willing to rely on Linux applications that stick to mobile friendly APIs.
You need to configure and compile your Linux kernel for aggressive power saving, of course. Seeing how Linux currently struggles to effectively do power management on laptops without S3 sleep, there's plenty of work to be done if you want to use it with a phone.
It's not just about app developers either, Qualcomm's modifications to the Linux kernel are public thanks to GPL but most phone kernel modifications haven't made it into the upstream kernel so far. Projects like postmarketOS are trying to make things better but it's not easy to port practical code that works into code that's acceptable for the maintainers of the broader Linux project.