Why I asked about having your own modem/router is because Sky try to force you into using the one they supply, which logs in using MER. (Nothing to do with Merlin).
Using your own is allowed, but AIUI they won’t tell you the username and password. (Unless that policy has been changed). There are plenty of posts explaining how to discover them, but whatever you use needs to support MER.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - AAISP Home::1 80/20. 200GB. Sync 70745/12295Kbps @ 600m. BQMs - IPv4