Could you elaborate on why you consider it not a good solution?

I can agree with that.

Assigning a name to a lambda function.

Which part?

Bad practice

Not a good solution, but a cool one.

Here the goal was to show how you can work with lambda and other python chips, so that newcomers learn something new.

It is bad practice to assign a lambda to a variable. PEP8 states that its an Anti-Pattern.
Just declare a normal function if you want to use it more than once.

See also: https://docs.quantifiedcode.com/python-anti-patterns/correctness/assigning_a_lambda_to_a_variable.html

Why bad practice? If this needs to be done, let's say in the key= or somewhere else like that. Here's an awkward example: arr = [(1,4),(2,3),(1,3)]; sorted(arr, key = lambda e: sum([*range(*e)]))

Bad practice, but clever :)

I know this works fine since Python uses lexicographical ordering but i think

int(str(today - last)[:2]) > cycle_length

would be "cleaner".