Dawn Wing Necrozma coupled with Prism Star Lunala played with Fighting Fury Belt and some cheeky Mimikyu tech is probably the easiest counter to Buzzwole GX, though we really don't need a direct counter to Buzzwole GX since anyone playing Tapu Lele can already OHKO Buzzwole GX. Any Buzzwole with 3 energy on it for Knuckle Impact gets OHKO'd by a DCE Tapu Lele GX (5 energy x 20 = 100 damage x weakness = 200), and if they have FFB then you just attach a choice band. From there you can 2 hit KO every Buzzwole that comes into play prior to them getting 3 energy. Buzzwole will never win the damage race against Lele only spamming Jet Punch, but I digress.
Dusk Mane Necrozma I think is a card that looks bad on paper (get it, cards on paper?) but honestly needs to be tested. Most people are leaning towards a 2/2 stage 2 Solgaleo GX split in the Solgaleo deck, which leads to a handful of its own issues in terms of consistency. Dusk Mane Necrozma's attack has the same "cost" as Sunsteel Strike on SuMo Solgaleo GX. Both of them discard 3 energy, which mean both of them have the same requirements for getting reaccellerated. It's just that Dusk Mane Necrozma has a higher "start up cost" with needing 4 energy to get going. Choice Banded, Meteor Tempest hits for 250 which is currently the highest HP any Pokemon can achieve in the game so far, so it really isn't a bad attack. SuMo Solgaleo's Ultra Road is great...if your opponent isn't playing Garbodor. Solgaleo Prism Star also makes the playing ground pretty even in terms of energy requirements.
Dusk Mane Necrozma gives the Solgaleo deck the option to play a 4/2/3 New Solgaleo GX line up and 3 copies of Dusk Mane Necrozma - New Solgaleo GX is your tank, Dusk Mane Necrozma is your sweeper. It's definitely not as streamlined as Ultra Road, but running better card counts might make the deck better simply through consistency.
Definitely worth testing.