I've been playing Civ 7 away from home recently, using the Steam Deck for a portable option. My major complaint with playing on the platform is that there is no option to go beyond a 1280x720 resolution when connecting the deck to an external monitor, even if the monitor is able to support higher resolutions. The main problem with this is that it means the game is locked into the more cramped UI, on top of the pixelated look given the low resolution. While this UI is understandable while in handheld mode, it's frustrating to use on a larger display that is able to support the full HD interface.
I initially sent this as a bug report, but was told by support that this is currently intentional on the deck hardware. They graciously said they'd pass the feedback to the team, but I wanted to post this here for others to be aware and reiterate that it'd be nice to see at least a 1080p option when connected to a display. I haven't run into this issue on any other game I've played on the deck, so unless I'm mistaken I don't believe this is a hardware limitation.