Author of the guide @Spokeek linked here - I’m thinking it might be that you’re running out of RAM or VRAM. You’ve only got 12GB and your swap file may not be particularly large.
Most modern Linux distros use ZRAM, which, in a massive oversimplification, compresses part of your RAM. In at least Fedora, this, by default, is half of your RAM with a maximum of 8GB, so in your case, that’d be 6GB.
This has the appearance of giving you an extra 6GB of “RAM” to play with, but in reality not everything can be compressed.
Compound that with the fact that integrated graphics share RAM with the system, and VRChat is very RAM and VRAM intensive (depending on the world and your settings in game), and you get crashing after a little while.
You very likely have something like 256MB-1GB allocated as VRAM, which means you get less RAM to give to the OS. The only fix for this, unfortunately, is to either get a dedicated graphics card (something like an RX 460 is pretty inexpensive and doesn’t require extra power. Just make sure you get the 4GB version if possible), or upgrade your RAM (which is super expensive even for a DDR4 system like yours).
However, this is all just guessing. If you want to test it, you could create an 8GB-16GB swap FILE in your root partition. To do that, run these commands:
sudo dd if=/dev/zero of=/swapfile bs=1M count=8G
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
Just know that at least RIGHT NOW it’s not gonna be persistent, but it works for testing (as in, it won’t work when you reboot), you need to add a line to /etc/fstab to do that: /swapfile none swap defaults 0 0