Ahh right, I'm getting about 4ish hours on my quite healthy battery on Mint, which felt short. I just fiddled about with TLP and dropped the discharge rate by half-ish. Otherwise it's a great little low-cost device!
Running Ubuntu on my 2015 air I struggle to get 2 hours out of it. I was able to get TLP to bring it close to 4, But it was at the cost of being borderline unusable.
I have a mid 2014 Macbook Pro still running Catalina, I wanted to change it into arch, but it saw very use and mainly my wife use it to watch movies so it doesn't really seems worth the effort.