Not a laptop, but I am livestreaming games from a Linux desktop. In the roughly two years since I've started doing this on a regular basis, I have played 23 games on stream using Steam Proton. My experience matches what Steam Deck owners told me about compatibility. It's not been completely glitchless, but all the problems I ran into were minor graphics glitches. When I buy games, I check protondb.com in advance, and it's always either Platinum or Gold for me these days.
I will note though that all the games I played were either single-player or cooperative multi-player. With competitive multi-player, there is an entire can of worms because of anti-cheat software. Valve's own anti-cheat should be fine, but if the game developer is using a different anti-cheat, it usually relies on Windows kernel drivers or some other shenanigans that conflicts with Wine in a major way.
I prefer linux to windows generally so the ability to game without re-booting is a bonus on top of that. If I preferred being in windows I wouldn't run linux just for gaming.
However most distros still install Grub, and (although not their fault) have a crusty UEFI boot sequence making that startup sequence worse than it needs to be.
Steam also haven't officially released SteamOS 3, so unless you are going to do a bit of modification, it won't quite be as slick.
On the other hand, even with all that it is vastly better than the Windows experience.
And yes, gaming on Linux has been infinitely smoother and gets leaps of improvements every year. We're at a point where unreleased games already play on Linux, and typically with better performance than naively on Windows.
Controllers, audio, etc, all play out of the box, perfectly, since years now
So, on day 3 or something of release, Linux was the best platform to play the newest AAA game.
The year of Linux gaming has been here for a while.
I'd hope that those issues eventually got resolved on Windows too...
* there is one caveat to that though - if you have a VR headset, then there are many people reporting performance issues on Linux with those headsets. And personally I also find VR performance subpar on Linux (although it still improved in the last year).
Longer version: https://www.retorch.com/blog/linux-mint.htm
The games I play like CSGO work very well*, you have a steamdeck so you know how game support especially with anti cheat is.
However, I've had many bugs. Nvidia on linux is painful. Just linux things - I get a bar at the top of the game when starting sometimes and have to change my resolution back and forth to fix it, I've had to restart pipewire to get my audio to reappear, I've had to replace pulse with pipewire (mid game).
Linux is not smooth, ESPECIALLY with nvidia. If the games you play are well supported, use AMD graphics, and doesn't tinker with their system at all, on a very stable OS - maybe you could call it stable?
Also if you want smooth - for the love of god don't use a rolling distro. If you check the arch wiki you'll see various nvidia/steam/wine/proton issues occur every few weeks. Many completely break playing games for several days unless you downgrade packages.
tl;dr - I would not recommend linux as a desktop to anyone who doesn't mind having their nose in their terminal desperately trying to figure out why you have no audio while your friends grow tired waiting for you.
The steamdeck specifically is very well managed by valve and I'm incredibly impressed that they made it work so well.
I've had a better experience since I switched from arch to ubuntu. For example steam remote play works w/ my Apple TV upstairs. Under arch I couldn't ever get it to work.
I've had mixed experience with AMD vs Nvidia. I bought a 5700xt which was way less reliable than my old nvidia 980ti, which never once crashed under linux. I upgraded to a 6700xt last year and that's been smooth. I'd originally bought the AMD card hoping to run Wayland but am still on X11.
I'm mostly playing single player games.
Let's assign blame to Nvidia, though. It's their drivers that are crap, it's their decision to keep their hardware so heavily NDA'd that others can't write good drivers for it.
I'm not going to excuse Nvidia - their driver is buggy and they're still missing DLSS3. Many of the problems I had were nvidia specific, especially anything touching wayland.
However my audio issues, or a bug where if you click the selection of applications when you alt+tab would lock gnome up and you'd have to kill the application from the terminal - those were not nvidia specific AFAIK.
I've also heard of non-smooth experiences from AMD hardware.
I don't think it's fair to recommend linux to anyone who would be scared off by the terminal.
I'm not at all saying it can't be relatively smooth sailing though, especially without a rolling os.