NowTV is exactly the same as Sky, was with them last year. You get a Sky IP address and they support IPv6.
They actually use DHCP for authentication, but don't validate the clientID anymore, in fact option clientid can now be completely omitted, or you can use a random value, however if present the clientid string must be hex encoded (no delimiters) for openwrt - eg use https://coding.tools/ascii-to-hex
There are only minor changes needed, the main one is selecting DHCP Client in WAN protocol and entering a clientID, and if you are switching from ADSL, then you'll need to add a custom interface "dsl0.101" under WAN->Physical Settings.
You can easily set it up in the UI, I think Bill's pdf guide covers setting them up in the UI apart from the IPv6 settings, but I've posted the relevant bits from my network settings file below.
config dsl 'dsl'
option annex 'b'
option tone 'a'
option xfer_mode 'ptm'
option line_mode 'vdsl'
config interface 'wan'
option ifname 'dsl0.101'
option proto 'dhcp'
# option clientid '613162326333653466353036406e6f7774767c6131623263336534' # EDIT: either omit this option or if included clientID must be a hex encoded string in recent openwrt versions.
# option macaddr 'AA:BB:CC:DD:EE:FF' # optional, clone your now/sky router wan mac if you have trouble connecting when swapping between routers.
config device 'wan_dev'
option name 'dsl0'
config interface 'wan6'
option proto 'dhcpv6'
option reqaddress 'try'
option reqprefix 'auto'
option ifname 'dsl0.101'
option delegate '1'