“After a link to the Dell forum post was ported to HN, the post mysteriously was deleted in the same day.”
Dell’s Latitude 5420, 7420 and 7520 throttle their CPUs hard on Linux, including Ubuntu builds Dell itself certified. Users had been reporting it on Dell’s forum since last year with no fix. The thread got attention and vanished the same day. Deleting the complaint is cheaper than fixing the firmware.