Help! "the software was closed because an error occurred"

A friend of mine installed Atmosphere on my Switch back in 2022. Last year, I managed to update both Atmosphere and the Switch to version 18.1.0. This year, I tried updating the Switch to a 20+ version and Atmosphere to 1.9.5 and Hekate to 6.3.1, and ever since, I've been getting the message "the software was closed because an error occurred" when I open any game. Today, I managed to revert the Switch back to version 18.1.0, but this message still appears for every game, EXCEPT for Mario Kart 8 (this message appears for both physical and digital games; I tested both).

I'm no longer in contact with this friend and I'm very new to this subject; I don't know what to do. (I also tried installing Sys-Patch 1.5.5, but it didn't help either).