Some original Switch games have had issues running on the Switch 2, be it crashes or stability problems. Portal 2 is one such example as the game typically crashed after updating. With the latest firmware update, Nintendo seems to have addressed some of these compatibility issues, even though the patch notes are as barebones as ever.
Nintendo released firmware version 20.2.0 that, according to the official patch notes, fixes the issue of Parental Control settings not transferring to the Switch 2 from the original Switch during system transfer, getting stuck on the “Searching for networks” screen, and brings general system stability improvements. What it doesn't state is the improved backward compatibility with some games.
Switch data miner OatmealDome noted that the update fixed Portal 2 on the Switch 2 and the game no longer crashes. The Nintendo eShop has been updated to confirm the game’s compatibility with Switch 2. Another user shared that Crypt of the Necrodancer now works as well and its store page, which deemed the game unsupported for the Switch 2 at least till July 8 (Wayback Machine snapshot), now says “Supported – Game behavior is consistent with Nintendo Switch.”
Some users noted that games like Age of Calamity and Slay the Spire work fine now as well. However, not all games have been affected and Borderlands 3 is still buggy, as shared by one of the commenters on OatmealDome’s post.
It's overall good news that Nintendo is working to make some original Switch games more stable and compatible with the Switch 2, but it would be more helpful if the patch notes had some indication as to what has been fixed.
Source(s)
OatmealDome on BlueSky, Nintendo US Store (1,2), Wayback Machine, Nintendo patch notes