引用自 Erdaron：

The game is consistently crashes within a few seconds of starting the Grand Regent fight. The crashes occur specifically here - if I don't enter the boss level, I can wander around and go back to camp without any issues.

No mods installed, presently or ever.

Is anyone else having this issue?

Searching the Discussions for these key-words reveals that this is the first time it's been reported.
Try verifying the game files within Steam, deleting the Settings.txt file inside the TL2 Save Folder, and also re-rolling the world with a Lan game.
And see if anything changes or remains the same.

Re-installing the game did not help. It still crashes in the same way in the same place.

Are there launch commands I can add to modify game graphics? Like turn hardware acceleration on / off, etc.?

引用自 Erdaron：

Re-installing the game did not help. It still crashes in the same way in the same place.

Are there launch commands I can add to modify game graphics? Like turn hardware acceleration on / off, etc.?

Yes, it's common for Linux players especially to use the launch commands within Steam to help the game not crash in some cases:
https://psteamcommunity.yuanyoumao.com/app/200710/discussions/0/4638238419731922295/

For older GPUs, the driver should work very well until 2020 and for new hardware there is too little information about which driver is better. If you're lucky, the latest one will also work.GL™

You can also try limiting the fps to a low setting. A lot of older games were designed to run at only 30 fps, because that's all computers could do back then. I've limited the fps on this game and a bunch of my other older games to 30 using the NVIDIA control panel and they all work much better with most of the major bugs and crashes resolved. It seems counterintuitive for those of us with gaming rigs, but it's worked very well for me.

If you use the same desktop resolution in-game, TL2 performs surprisingly well.

Had the exact problem as the OP. Fixed it by turning resolution way down for that fight.