About 8 hours. That is the biggest sacrifice I make by not going with a Macbook. But fwiw I'm on Arch, I haven't spent any time on battery optimization config. I'm sure I could get a few extra hours if I played with the configs.
It's not exactly comparable to my MBP, but neither is the cost! The FW cost me about $1,100 all-in and the MBP was $2,900 (both 32GB/1TB).
1: https://knowledgebase.frame.work/optimizing-fedora-battery-l...