I’ve had a set of Hand Ups, a set of Specialized “gravel gloves”, and some set of Giros and have had varied luck, mostly surrounding removing skin between my fingers to the point of bleeding. This usually happens in races under 5 hours, I’m looking to perhaps get into some 24-48 hour races this year.
Some motorsports gloves are reverse stitched for this specific reason, I’ve never seen a reverse stitched MTB glove though, and would settle for flatlock.
Oh, and those conductive fibers so I can use capacitive touchscreens is a must as well.
I’m a big fan of the Rapha Brevet gloves which aren’t designed to be warm, but I think they’re going to have the same seam issues you’re describing - I think I’ve probably stopped wearing mine for similar reasons without realising it.
There was a time where I couldn’t deal with structure-less gloves made of that slightly stretchy softshell or roubaix fabric because it felt like my hands just slid around too much within them, but in the last couple years I find they’re my preferred type by far. I don’t know if maybe my bike fit and/or core strength have improved or if I’m just more comfortable with that interface now, but I no longer feel like I’m sliding within them. The softer fabric means the seams are a non-issue for me as well.
I have and like a couple pairs of Rapha Pro Team gloves, but after finally deciding I really like them I realised they’re actually nearly identical to a years-old pair of Pearl Izumi gloves that I got cheap for short commutes.
These lightest fleecy/softshell gloves usually come with me for ultras and I’ll wear them from like dinner til breakfast when it’s cool out, but then I tend to just ride with bare hands or fingerless mitts during the day. I can’t recall ever feeling too hot in them but they definitely aren’t designed for hot weather.