https://www.dsogaming.com/news/diablo-2-resurrected-technical-alpha-has-been-cracked/
If even the cracked version of the Technical Alpha still requires the B.net client then I guess it's safe to assume that it will be the same for the final release version as well. A shame, but this (+ all those little deviations from the original, especially in the characters' design) only makes it more easier to give Ressurected a pass, at least in my case.
In regards to Legacy Diablo II + LoD getting a release on GoG sometime in the future, I still think that's in the realm of possibility. Simply because Blizzard might not want to support/keep maintenance running for the standalone original release forever and the standalone original release likely won't sell that much anymore once the remaster (which comes with the built-in Legacy version) is released.
And considering how exceedingly well Diablo I performed on GoG Blizzard would be stupid to not repeat that with a DRM-free release of Diablo II + LoD here as well.
Time will tell.