exchange french
Possible justification of playing 1. e3 as white

usually e3 goes with english opening lines, or colle system. But e3 can also aim for nimzo larsen kind of structures, with pawns on b3 and e3. The van't kruijs opening is far from being garbage

In more seriousness than my above post, I definitely wouldn't call 1. e3 "hot garbage." It's just an equal chess opening, like the Nimzo-Larsen or the Orangutan or the KIA or whatever and you won't lose because of it (altho if you're a master you might struggle getting any advantage as white consistently).
Say like 1. e3 d5 2. c4 first of all, that seems reasonable esp for someone like me who has sometimes played 1. Nf3 2. c4 or 1. Nf3 d5 2. e3 and 3. c4. I'd play this, but you could also play 2. d4 and transpose into a Colle, or of course 2. Nf3 would transpose into a position I've played before pretty often.
1. e3 e5 and you have a choice. You can play 2. d4 and now black should probably take it (since 2...e4 3. c4 is nice), after which we transpose into an Exchange French which is equal but some players like to play this opening. Or you can play 2. c4 and that's a type of English, or 2. b3 and that's a type of Larsen.
1...Nf6 is flexible but so was 1. e3, so white can play any of 2. b3, 2. Nf3, 2. d4 or 2. c4 with an equal position and then play positional chess.
I know not much of the book was about 1. e3 per se, but there's a reason "e3 Poison" was a thing. It's not a bad idea. No it's not ambitious but "the position is not equal if the players are not equal." And if you want to take your opp out of prep and just play a chess game based on understanding I actually think you could do a lot worse than 1. e3.
Also food for thought: the game of chess clearly ends in a draw with best play after 1. e4, 1. d4, 1. Nf3, 1. c4 etc and 1. e3 is the same. So that being the case, I've often considered that maybe the entire concept of "advantage" is subjective (because someday in the far-off future there could exist 32 piece tablebases and such) and maybe it's just all a question of putting practical pressure on the opponent and making them find good moves consistently until, after enough errors, it becomes winning. Which is what chess should be all about anyway: outplaying the opponent from a chess position.
More food for thought, perhaps the invention of the neural network is (well, the engine started, but the AI finished) completely, wholly, and irrevocably ruining chess.
Chess 100 years ago was two intelligent men sitting at a board opposite each other, each armed only with their knowledge and their ideals. Sacrifices were common, all openings were fair play, gambits abound. A great time for chess, and what a show it was to watch!
Chess now, however, is dying. The ELO inflation as the flood of young, engine-prepped masters is only beginning, the death of classical openings from the King’s Gambit to the Ruy Lopez (and with it, soon I suspect e4 as a whole will fall), the slow collapse of correspondence chess and the even slower collapse of classical (hopefully during neither of our lifetimes. That may well be too much to ask), this newfound need to play “this brand new gambit nobody knows” or “trick openings to take your opponent out of prep”. What happened to the days where you and I could sit, shake hands, and play chess, fresh out of prep in the Ruy Lopez as soon as we reached the Ruy Lopez? I think chess is dying. I think Gen Alpha (Gen AI more like) will finally be the ones to kill it.

Personally I find the justification of e3 of “my opponent doesn’t play e4, but I’ve been itching for a good Marshall Ruy Lopez from Black’s perspective… maybe if I play e3 they’ll play e5 and… yes! 2.e4!! And flip the board! It’s Opposite Day! Black is White! White is Black! Screw you d4 player!” VERY amusing, and also viable as long as you know how to deal with the consequences otherwise. Granted I find it amusing because I’m a sadistic bass turd, but ehh, we all have our flaws.

Sorry that was d3, not e3
Terrible game. You were White? You hung a knight, two pawns, your queen (he missed it) and got lucky he missed your mate threat. He hung his queen, you missed it, he hung it AGAIN, and then hung mate.

I won; that’s all that matters. And I beat an 1800 player playing one minute bullet game. He’s the one who played terrible, not me.
Ahhh, bullet? I rescind my statement and would like to humbly apologize. That’s actually quite a good game for bullet for your rating, nice win

E3 might not be very challenging, but it’s certainly playable and you might get and exchange French lol
Here is a possible justification of playing 1. e3 as white. In a specific scenario, if your opponent never plays 1. e4 as white and you have at least a pretty good understanding of 1. e4 1.e5 positions (and fine with a few transpositions to the QG or English as white), you could play this to throw your opponent off. Since your opponent wouldn't play e4 as white and if you have solid experience in e4 e5 positions I assume you could take advantage of this considering your theoretical opponent never plays e4 as white. If your opponent plays 1. d5 then you just achieve a normal position. It's also helpful if you are experienced in the Queens Gambit as white and want to have a possible opportunity to throw your opponent off their game with a reverse e4 e5 position. (There are also positions that can transpose into b3 positions with this opening and many top games have started with e3.) Thoughts?
My thoughts are this has to be the dumbest justification for an opening I have ever heard. You're literally now black for the entire game - no that's not a reasonable thing to do.
I think there are in theory legitimate reasons for playing 1. e3, it would be generally followed by d4 at some point.

1.e3 and 2.d4 seems quite logical for a player who loves the French Defense as Black, and the feel of those positions.

I dont get it why people promote this move. It is simply inferior to the normal opening moves. With white you should try to put some pressure on your opponent. I understand that someone plays an inferior move in order not having to learn a ton of theory but here this is not the case as black has many ways to respond.

No, but if someone asks about this move he should get an honest answer: this move is bad, not because it will result in getting a worse position but because there are clearly superior moves available.
There are many other opening moves which are not optimal but they all have some advantages to make up for it, 1.e3 doesn't.

e3 is definitely alright. Could transpose into a lot of different openings or you could play a reverse French a tempo up. It isn't the best but it does not give a weakness. Just space advantage for black.

Quality chess has a book e3 poison, which considers 1.e3 and e3 after other points in opening. It's completely sound, and can use move-order tricks to get structures more familar with than opponent. For example looks at e3 in the english, and 1.e3 e5 2c4 is one possible way to arrive at these positions.
1. e3 is a trash move, play 1.e4 instead. It is really simple.