how do I know if my MacBook was jailbroken?

As a side note, if your Mac was ever to get truly jailbroken (at the firmware level), that would require putting specialized/hacked firmware onto the M1 chip inside your MacBook Air. That process requires physical access to your Mac, and it would likely erase all data.

There are legitimate, Apple-provided ways to modify macOS system files (not the firmware), but doing so would require physical possession of your Mac, and your login password to change the secure boot policy. Also, the next macOS update would undo those changes.

If you are still concerned and want to be absolutely sure that your Mac is running known-good firmware, back up your data with Time Machine, and then follow these steps to revive the firmware in your MacBook Air using a second Mac: Revive or restore a Mac with Apple silicon with Apple Configurator 2 - Apple Support

Hi there! I can explain this. This is a false positive as the app in question has not been fully updated for IOS 14 compatibility. I would first see if there is an update for the app in the App Store. If there is not, I would contact the developer and let them know.

As a side note, as long as you didn't try to jailbreak your Mac, you are all good