TL;DR for LCD: Preview “OLED” firmware appears to improve the input lag with LCD models, too

[…] I consulted Valve about this who recommended updating the LCD firmware to the preview firmware, which should bring parity in software between the two units. This changed the results to what you saw above, but either something was wrong with my Deck, or else all LCD owners are also going to get a noticeable improvement with the new firmware, as you can see from the tables below.

Valve did share with me that they’re looking to improve input lag, and assuming these older firmware results aren’t a problem of my LCD Steam Deck, it seems that owners of the existing machines should be seeing a nice improvement to response, particularly when those all-important frame-rate caps are used.