DavidKok, on 2022-December-05, 09:04, said:
1♦-1M; 2NT is 6(+)♦, 3M, strong (the BW death hand - it depends on partnership agreements whether you want this to be GF or just forcing to suit agreement at the 3-level. My preference is GF), though with an unbalanced diamond I think it's better to play Gazzilli so that this becomes a specific type 4-card major suit raise.
1♦-1NT; 2NT is stronger than 1♦-1NT; 3♦.
1♣-1♦* (Dutch Doubleton); 2NT does not exist (a 1NT rebid would have shown 17-19).
1♣-1M; 2NT is 17-19 balanced GF, since 1M promises 8HCP (although we may upgrade for this bid).
1♣-1NT; 2NT does not exist (17-19 balanced bids 3NT, hands with clubs bid 2/3♣ or their second suit) but I suppose it should be a soft 3♣ rebid.
It has become increasingly popular to play 1♣-1M; 2♦ as either 17-19 bal or a real reverse, with 1♣-1M; 2NT showing the BW death hand. I think this is an improvement.
But most importantly, the point is not to make some clever use of the 2NT rebid, it is to stay low on the 19 opposite 4-5 point hands. You can fill the 2NT with any artificial hand (GF long minor or GF artificial raise are popular) once it's freed up.
Edit: I forgot to include the major suit openings. 1M-1X (so NT or 1♥-1♠); 2NT shows 6M4m GF, part of standard Gazzilli.
We play 4 card majors so the structure is different, but 1x-1y-2N covers all 4 card GF raises of partner's suit except 4441s, BW death hand and huge 6-4s.