The GUI version of Timeshift offers the ability to automatically keep the last X backups:
https://raw.githubusercontent.com/teejee2008/timeshift/master/images/settings_schedule.png
As far as I can see, there is no such option using CLI:
https://github.com/teejee2008/timeshift#readme
https://manpages.debian.org/testing/timeshift/timeshift.1.en.html
Is there such an option using CLI?