How about this challenge:
Shoot daily with a single lens the whole month.
It can be any lens you like or want to get to know better.
In my case it will be a fastish moderately wide prime, the Z 35/1.8, on my Z 6II.
For you, it can be anything you own... Maybe a kit zoom, or a fast zoom, or a tele zoom, or a fisheye, or a superzoom, or a macro lens, or a prime of some other kind. Shooting with something super quirky might be fun, but maybe more suitable for a shorter challenge.