At the risk of being “that guy”, my solution was to buy an M1 MacBook Air.

At some point you have to accept that there is no one in the linux space incentivized to create a modern desktop experience, much less laptop power optimization comparable to a “vertically integrated” player like Apple.

I would love to get Apple hardware and battery life running Debian. Maybe Asahi will make it happen. In the mean time, I’m enjoying 99% of the things I like about Linux, with none of the massive pain wading through forum posts trying to figure out what bitman97 did back in 2015 to get their backlight to work with the Debian stable kernel

I saw massive differences in window managers. Every Linux machine I have beats windows in battery life by a very large margin iff I use i3. With default (‘nicer looking’ depending on taste) they do far less. Like my 2011 x220 still does 15 hours on i3, gpd pocket 1 similar, Pandora gets 20 hours, etc. The ones that run Windows, like the pocket and x220, barely make 4 hours. Note that I did optimise the Linux and did nothing to the windows installs, but still. I have a stack of laptops with dual boot from Dell, Acer etc and I have the same results there; far shorter than the above go to machines, but windows less than half of Linux for anything I do.

Best solution I have seen is to buy a Chromebook and install galliumOS. Still has most of the same issues as any desktop Linux but at least has all the power saving features of chromeos are included. That way you don't have to buy a device from a company that decides to throttle the CPU when they want you to buy a new computer.

I once bought a windows ultrabook for on the road, with a 128gb ssd. When I unpacked the computer 90% was used by the operating system. It was basically useless. I installed Linux and only 6gb was used. I had no battery issues. I could use apt install. Life was beautiful.