Some of the rental hardware no longer allow users to login as admin. Some of the ones that do the ISP landlords make a lot claims that leases/monthly fees go up if they think to try. There's a growing disparity between modem/router hardware owners and "this lease seemed like the best deal from the cable/phone company" average users.

I have "business class" service from a provider (Canada - Rogers), which came with a "Clearnet" router/wifi combo that has, LTE failover. (Cradlepoint)

And - of course it was locked for admin - well - not for long, the technican who installed it gave me the password after we chatted for awhile. Admitedly, I cannot change the PW he gave me, and at some point if they remotely update it, it will stop working.

Now they make you manage the very limited subset of router options (essentially SSID and WPA passphrase) from their web portals. Then they push the updated configs to your router via remote management protocols. How many vulnerabilities do those open?