How to prevent g8-a2 diagonal weaknesses in Leningrad Dutch?

Against d4, I played King's Indian a few months ago. But it's knight manoeuvres for attack seemed a bit tricky to me. Hence, I decided to switch to comparatively more aggressive option, 1...f5. I often get good position but, whichever game I lose is just because of g8-a2 diagonal weaknesses. I mostly get struck in Qb3 lines after c4. I just wanted to know if there is someone who knows well can help me with this problem.

The problem I stated above is the main, but I would be very thankful if someone also tells me how to fight against Hopton Attack  (2.Bg5).

That is the problem with the Leningrad Dutch and why it is dubious. If you don't want something that is borderline dubious, then you must avoid defenses like the Chigorin, English Defense, Leningrad Dutch, Budapest, or Modern Defense, and surely avoid the unsound Englund or Albin.

If you want a Defense that does not have major issues like the a2-g8 diagonal in the Leningrad, the following are basically your options:

QGA

QGD

Slav

Semi-Slav

Kings Indian

e6-Dutch lines (Classical, Leningrad, Modern If no g3 by White)

Grunfeld

Nimzo-Indian with the following options after 3.Nf3

- Queen's Indian

- QGD

- Modern Benoni*

* Note that the Benoni is best played in conjunction with the Nimzo. 1.d4 c5 is dubious due to 2.d5 and Nc3 and e4 (NO c4 by White) while the 1...Nf6 and 2...c5 lines are also dubious due to the flick knife attack, something that cannot be done once Nf3 is played before f4.

In the case of the QGD, NID, and e6-Dutches, if you are a French player, you can play 1...e6 first, avoiding things like the Trompowsky, Levitsky, or gambits against the Dutch. Then if 2.c4 or 2.Nf3, you play your normal 2...d5, 2...f5, or 2...Nf6, depending on which defense you are going into.

Against 2. Bg5 simply 2... g6 should do fine (eg 3. Nc3 Bg7 4. e4 fxe4 5. Nxe4 d5 doesn't look all that great for White). 2... h6 is clearly critical, but lots of traps and theory. Also it's not a good idea to play a line pushing all the kingside pawns, Dutch and King's Indian players already love pushing the kingside pawns way too much (ie they do it when it's good but also when it's bad, mainly because, hey, in a sharp position with lots of pieces, there are always chances to get away with it).

Nerwal is giving away the secret. The Hopton attack is like a cheatcode for lower levels, it's so easy and straightforward to play, but fianchettoing the black king brings white back to square one again.

To answer the question, you can’t prevent it, you have to learn to live with it. All defences, especially active ones, have some down side. If you make a mistake, that is usually what your opponent can exploit. If you go wrong in the Nimzo-Indian, white’s bishop pair will mate you. If you go wrong in the Grunfeld, white will ram his d-pawn down your throat. If you go wrong in the Benko, you will just be a pawn down. If the Leningrad is dubious (which I think is an exaggeration), it isn’t because of this weakness. The Najdorf and the Sveshnikov are two of the soundest defences to 1.e4, but both leave a gaping hole on d5.

Why is the e6 pawn move followed by f5 a better Dutch?

"The Najdorf and the Sveshnikov are two of the soundest defences to 1.e4, but both leave a gaping hole on d5."

They're two of the wildest that are playable at the elite level, not the soundest. The soundest would be the french, caro, morphy, berlin and petrof, not Najdorf and definitely not the Sveshnikov.

“Sound” doesn’t mean “safe”. Its meaning is more or less “playable at the elite level”.

It isn't better, just different. You have to look after black square weaknesses, rather than white square weaknesses. It is probably safer but less ambitious.

Vulnerabilities on the a2-g8 Diagonal (against Qb3 after c4)
The main issue you're describing happens after you play the Dutch Defense, especially after White plays c4 and then pressures the queenside with Qb3, targeting the b7 and a2 squares. This pressure is a common tactical motif in such positions, and here are a few ideas to counter it:

Development and Counterplay: One way to deal with Qb3 is to avoid weakening the queenside too much. Often, Black needs to be proactive with piece development, especially with moves like ...Nf6, ...Be7, and ...d6. Sometimes, preparing a counter-push with ...e5 or ...c6 can help neutralize the pressure.
Move Order: The timing of ...c6 can be crucial. In some lines, you might be able to push ...c6 to challenge White’s d5 or b5 advance, preventing White from using Qb3 as effectively. Also, the move ...Nf6 can support the critical d7 and e5 squares, preventing White from generating too much pressure on the queenside.
Exchange Ideas: If White plays Qb3 and aims at the a2 square, sometimes the idea of ...Bf6 (or ...Be7) to support the g7-pawn while moving the knight away from f6 (in case of Ng5 or Qb3) can help. You can then play ...d6 and counter in the center.
Piece Placement: After ...c6, if White’s queen comes to b3, the idea of ...Qb6 (trading queens) is sometimes a valid idea, as it helps neutralize the pressure on the a2-g8 diagonal.
2. Against the Hopton Attack (2. Bg5)
The Hopton Attack (2. Bg5) is a tricky setup aimed at putting immediate pressure on your knight on f6, which is common in the Dutch Defense. Here's how you can handle it:

Early e6 and h6 ideas: You can try ...e6 (preparing to develop your bishop and keep your pawn structure solid) and sometimes follow it up with ...h6. The move ...h6 aims to drive the bishop back and prevent White from following up with Bg5. If White takes on f6, you can recapture with the queen or the g-pawn (depending on the position) and try to use the open g-file.
Fianchetto Setup: A common response in the Dutch is to go for a ...g6 setup, fianchettoing your bishop to g7, which often provides a solid structure and pressure along the long diagonal. Against 2. Bg5, this is often a good way to keep your knight on f6 safely while still developing the rest of your pieces.
Development with tempo: If White plays 2. Bg5, you can often gain tempo by responding with moves like ...Nf6 (developing the knight), ...Be7, and then preparing to play ...h6 or even ...g5 depending on White's response. The goal is to trade off some pieces (the bishop) or undermine White's setup without compromising your position too much.
Counterplay in the center: You can look for counterplay in the center with ...e5 or ...d6 and ...Nf6, or even consider ...c6 ideas. The key is not to get too passive or overly focused on defending the knight on f6, but to look for active breaks or piece trades.

Don't blindly use ChatGPT unless you can understand why what it spews out is garbage.

Because it avoids the garbage lines.

No 2.Bg5 (Black can simply capture the Bishop)

If 2.e4, then 2...d5. No Staunton Gambit. Instead, you are in a French.

If 2.g4, you do not play ...f5 and White's position is ridiculous.

If 2.Nc3, then 2...Bb4 removes all the fun from Jobava Players. Only good move for White here is 3.e4, then 3...d5 is the Winawer French.

With 1...f5, the Staunton Gambit, Poison-Spike Gambit, 2.Bg5, and 2.Nc3 are all very annoying for Black.

If White plays 2.c4, 2.Nf3, or 2.g3, only then 2...f5, entering normal Dutch lines. If White plays an early g3, you play the Classical or Stonewall (personal preference - I play both). If no g3, then it depends on the knights. If d4, c4, Nc3, and Nf3 are played, where Nge2 is no longer possible, then 4...Bb4. Otherwise, 4...b6.

Did he really used ChatGPT to write that? What a joker.