I'm writing this, mostly, because there is zero documentation on this, and via Google, there is exactly one person having this same issue.
I believe it stems from a combination of Pop!_OS, Steam's Proton, and Vulkan shaders. Somewhere in that mix, there's an issue where the game isn't releasing memory, and on a random number of game state changes (loading screens), you'll just crash. The game will close, and since there isn't a sane quick-save system built into The Sims 4, this is usually catastrophic. Unless you're got muscle memory on slapping Esc > Save every couple of minutes.
Most don't.
Basically, I switched to older version of Proton. I switched to Glorious Eggroll, and I switched to CachyOS via ProtonPlus. No luck!
Then, I tried these two launch options:
* 1: AMD_VULKAN_ICD=RADV
* 2: PROTON_USE_WINED3D=1
And only the second one seemed to make some sort of difference. For a time. But it really seems like the crashing is completely random.
Sometimes you can go through 15 different game state changes with no crashes, and then on the 16th, CRASH. Sometimes you can load into another world, enter CAS, exit CAS, and then it crashes.
There doesn't seem to be any rhyme or reason for why these intervals are so infrequent, but I do believe it's entirely related to Vulkan and memory issues, and maybe Pop!_OS.
I've seen other users reporting that they're fine on Mint, on Debian, and even Arch.
Problem is, System76 only provides their drivers (which you need if you have a System76 PC) for, like ... Arch, Fedora, and Windows 11???
So, if you were to switch to Debian, for example, good luck getting all the drivers you need on your 76 PC. Because, even though the company states that you should "take ownership" of your system, you've gotta be some kind of wizard level Linux user to have a fully functioning System76 PC on anything but Arch, Fedora, and fuglucking Windows.
And people who follow me know by now, I am not switching to Windows, or even dual-booting, for one gotdamn game.
The good, thing, though, is that this seems to be the only reason the game ever crashes.
I can pause Sims 4 for ... say, six whole entire hours, and nothing will happen. I can spend all the time I want with a group of sims on one lot, and it appears no crashes will occur. Not until, funnily enough, you hit the barrage of loading screens EA has stuffed this game full of.

Currently, the only solution is to just save the game a lot, and prepare to have to relaunch if I feel like continuing.
But, for what it's worth, this is the single post on Reddit I could find where someone was having the near exact same issues as me.
I suppose, though, the only real solution is to wait for Pop!_OS, or Proton to be updated again, and then see if the issue is resolved.
Yay.
Source: https://mkultra.monster/gaming/2025/08/17/sims4-broken/