Is there an option to not get their router and thus waive the 1-year clause?

Otherwise what you mean is "it is mandatory to lease their router even if you have your own, and you are forced to enter a 1-year minimum contract.".

> Is there an option to not get their router and thus waive the 1-year clause?

Yes. you also have the option to just pay for the ISP router outright.

Oh that's nice! I asked because here in Spain they advertise the same, but you cannot opt out of getting the 1-year lock-in in any way.