Dug an old laptop out of the closet for Klipper and it works great

Did the same thing with a beat up ThinkPad that had a cracked hinge and a dead battery. Threw Linux Mint on it and it's been running my printer for about eight months now. The battery being shot acutally turned out to be a bonus, it acts like a built in UPS so a brief power blip doesn't reboot the whole thing mid print. The lid sleep thing got me too. I ended up just disabling sleep entirely in the power settings rather than messing with lid closing behavior, since I only ever close it halfway to keep dust off the screen anyway. Hinge is held togehter with a zip tie at this point but the machine doesn't care. One thing I'd add is to plug your webcam and the printer into diffrent USB ports if you can. I had both on the same side and got random disconnects til I split them up. Also found the laptop runs cooler with the screen brightness turned way down, wich barely matters since I'm mostly looking at it through Fluidd on my phone or tablet anyway. The gcode preview alone sold me. Caught a support issue on a tall print that would have wasted three hours of filament before I even started it.

I gave this a shot last winter with an old HP that was gathering dust, and my expirience was rougher. The thing ran hot and that little fan spun up like a hair dryer every time I opened the Fluidd dashboard, which got old fast since the printer lives in my office. I ended up wiping it and moving to a Pi 4 instead, and the noise problem just vanished. Cost me about sixty bucks but the silence is worth it to me.

That said, the laptop did teach me one thing I still use: I run the Pi headless now and just pull up the interface on an old Fire tablet I mounted on the wall next to the printer. Best of both worlds, no screen baking next to a hot printer and no fan noise in the room. If anyone else goes the laptop route and the fan drives them nuts, dropping the CPU to a lower power mode in Linux helped a lot before I gave up on it. Klipper does almost all the heavy lifting on the printer board anyway, so the host barely breaks a sweat during a print.

Mine's been on a decade-old Dell for close to a year now and the one thing I'd flag is to turn off automatic updates, or at least schedule them. Mine restarted itself mid print once because an update ran in the background, and that's not a mistake you make twice. Also check that the webcam stream resolution isn't set higher than you actually need, since I found dropping it made the whole dashboard snappier. The couch calibration sessions are real, I've done more input shaping in the last month than in the previous year.

Glad the lid thing wasn't just me. I went the systemd route and set HandleLidSwitch to ignore in the logind config, been solid for months. Also second the webcam port tip, my second camera kept dropping until I moved it to the other side of the laptop.

Ran mine off a discarded Chromebook that nobody wanted anymore, and the thing that actually made it livable was a cheap stick of RAM I had in a drawer. Stock it was swapping like crazy whenever the bed mesh graph loaded. Bumped it up and suddenly Fluidd feels instant. Only other thing I did was take the keyboard apart far enought to unplug the internal battery, since a swollen pack sitting next to a hot printer worried me. Runs cold now and has been up for about five months without a single hiccup. Curious if anyone's tried hooking the laptop screen up as a standalone status display instead of just leaving it open.

Update: pulled the laptop off the charger test after reading the dead battery as UPS comment and mine kept the printer alive through a short flicker, so that's a win. Killed auto updates too, that mid print restart story scared me straight. One thing though, mine runs warm like the HP poster described. Anyone found a way to keep the fan quieter without the thing cooking itself?