Not entirely sure if it's a Steam Deck bug or maybe an odd connection issue when I play on Steam Deck, but even in Single Player, which is single-player server (still online, which why????), you can still lag heavily on a single-player playthrough. All last night, I was mining, and a TON of times the little bar that depletes when mining was lagged by at least a second or more. Also, when going through warpgates, sometimes it would take more than 10+ seconds to even go through; also to this: as well as manually using your warp-drive to travel. Sometimes it could take more than 10+ seconds (even seen more than a minute) just to be able to finally "jump".
I get that this game was most likely built as multi-player and such, but still, many players such as myself play singleplayer. And to LAG on singleplayer? WTF. Come on.
I understand singleplayer starts a single-player server start. But seriously, there shouldn't "need" to be any connection whatsoever to the Steam or your servers if playing singleplayer.