[Q] Router DNS question

Hi, I'm trying to figure out how to set up a service like pi-hole and one of the prerequisits seems to be to have admin access to the router to make the correct DNS entries.

Unfortunately, the router provided by my ISP doesn't grant me access to these settings - is there a way around that, and what would it involve? I do have a hybdrid router (DSL + LTE connection), that's (according to my ISP) the reason DNS settings are locked.

Any ideas are welcome :)