Yep:

- External drive with a bootable backup (Carbon Copy Cloner)

- Network drive with automagical Time Machine backups

- Offsite versioned backups (for example Backblaze)

"Pride goes before destruction, and a haughty spirit before a fall", but I'd be surprised if I ever will lose a file like this.

Are there any versions of malware that sit and wait for several months so that once you have it in your backups it sits and waits for you to save over your old back up and then starts it’s thing? Then if you restore from that backup you have the malware sitting waiting again to start.

How would that work? If it didn't encrypt your active storage, then the backups wouldn't be encrypted either, right? Or would it somehow interfere with the backups, making you think the backup's OK when it actually is just garbage and then encrypt your active drive when no more usable backups exist?

I guess that's one reason why if you don't try restoring from you backups it's as good as not having any...

Can that be worked around by having extra backups with only non executable files? Like txt, png, cpp (but without compiling and running)?

I have a vague memory of ransomware that waited for one to mount external disks yes, but not as advanced as they ones you mentioned