> RAM (I think only 8 GiB, actually) or CPU (I don't even remember which Intel CPU it had Sounds like you had one of the cheaper T14's, it's likely you didn't

> RAM (I think only 8 GiB, actually) or CPU (I don't even remember which Intel CPU it had Sounds like you had one of the cheaper T14's, it's likely you didn't run into any power limits due to that. 1080p screen as well, I presume? Kubuntu 20.04 and its kernel version certainly throttle power on the higher-end T14's I've seen. If that's lifted then they throttle thermally, unless you manually force both cooling and power limits higher. Windows handles it all tad better, but the battery life is nothing to be amazed of.