That's simply not true. I have been daily driving asahi for 2.5 years or so now on an M2 Max macbook. In it's been one of the most reliable and smooth experiences I have had ever using linux. DP alt made is working fine for me. I'm not sure about battery, I never measured.
If we overlook battery life and DP alt mode being funky, crucial for laptop use, it becomes essentially a desktop tethered to the desk.
Do you actually use dp alt mode and not HDMI for external displays? What DE/WM are you using your mac with?
I use DP alt mode and also the HDMI port to drive two screens. I use hyprland and runs fine after configuration.
My battery certainly last a few hours. I use it as any other laptop I had before and use it daily on trains. So I cannot at all agree with your POV that it's a desktop. The battery is working without problems.
Do you know how M2 support compares to M1? Trying to figure out if M1 is the better choice for a used macbook to run Asahi on.
It's essentially the same. Afaik there is no feature the M1 has on asahi that is still missing on M2.