You're not alone with the cooking laptop in a bag running Linux issue. I had those in the past with Dell/Toshiba laptops in the past.

Dell Windows laptops will also cook themselves. (For example: https://www.dell.com/community/en/conversations/xps/dell-957...)

Macbooks are the only device I would trust to not light a bag on fire…

Anecdata but I've had a MacBook do the cooking once, but it thermal throttled itself so it just got warm, not super hot.

Yeah I once had my old Macbook Air get insanely hot to the point it felt dangerous. I left it in the sink (dry and in case it blew up it would be somewhere non-flammable) to calm down and it was fine a few hours later.

It's funny but sad how this has literally been an issue for 20+ years and yet still no one can fix it. I've tried with many laptops, both Windows and Linux, and the only one that can reliably go into a backpack with >90% charge and come out after a flight with >80% is a Macbook, and that's also been true for more than a decade.

It does feel like Linux sleep is nearly impossible to do well. My go-to example of jaw-dropping, industry-leading Linux hardware support is the Steam Deck. They deserve lots of praise for the monumental effort and achievement to make that product work as well as it does. The sleep functionality is trash though, even after they put a ton of work in.

It’s excellent in that I can suspend any software and have it come back to life exactly the way I expect (no small feat!) and it’s excellent that it never cooks itself when unattended in a case or bag, but it is total trash that it eats 20-30% battery a day while “off”. That’s not a bug, but expected behavior. It’s just not what I have come to expect from a modern computer, and portable Macs haven’t behaved that way since about 2005.

my only datapoint here is that I have a Thinkpad X1 running Debian that doesn't cook, and keeps a charge, but I have no idea how I pulled that off

Is this going to sleep? Or hibernate? I found that most notebooks(under Windows) are horrible at "sleeping", but if you enable hibernate, then the notebook can last days, without losing charge. (Dell, HP, Asus, etc.)

Another counterpoint, I have that same not-suspending-thus-cooking-in-my-bag issue often with a thinkpad P14s running windows 10 (intel i7-1270p) .

However, my (5+ yrs old?) T480s running linuxmint never does it (i5-8250u). YMMV