The Notes are saved on "my mac" only, and I do not have them on iCloud or anything else. I don't have any backups for Notes either because I never thought they would disappear.
Is there any way that I can get them back?
MacBook Air 13″, macOS 11.1
Probably worth a try to see if they were moved to iCloud, even if you weren't using it. I have no idea if it does that or why it would, but since you don't have any backups, that's the only thing I can think of.
Go to iCloud.com and log in with your AppleID that you used to sign into iCloud on your Mac. If you haven't signed into iCloud with your AppleID on that Mac, then there would be no way to have moved them into iCloud.
My Notes disappeared after upgrading to Big Sur, how do I get them back
