> X1 took 120s, so 4.5x slower… totally unexpected

Your numbers are clearly suspicious. Did you ever take measures to circumvent the CPU throttling bug under Linux on your X1E? See [1].

Also, regarding your battery comments, when my X1E G1 was new I got great battery life, around 7-8 hours. I still get 5ish.

> requires LUKS full-disk encryption, and having it setup conflicted with NVidia’s proprietary driver.

This just seems bizarre and hard to believe to me; once mounted your LUKS drive is no different (to software) than any other block device.

[1] https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Extreme#...