Question: Best choice of opening, if you are weak in solving tactics ?

There's no opening choice that would forgive tactical weaknessess... If you are weak at tactics, keep solving problems. But lichess trainer is not very good for this.... they always give you problems at the very end of your skills, this is not good to learn basic patterns. Chess.com has a better tactics trainer.

Openings other 1.e4 tend to delay when tactics start to happen. Games last longer which might lead him to think he's doing better with other openings. If he thinks that, he's mistaken. Got to have some tactical proficiency if he's going to succeed at chess at all.

french defense exchange, but there will always be tactics with any chess opening, just don't play the Sicilian if you dislike tactics and positional.

with d4 there are less gambits and tactical traps in the openings.

In open games (1 e4) the tactics happen early and fast and are right out in the open. In the more "positional" (1 d4, etcetra) closed games, the tactics are still there, just hidden and harder to find. Which makes them more dangerous, seems to me. Karpov had to know his tactics also, to see that if he pushed a2-a3 then zap, zap, wham, and the opponent has a knight on c4. People call that positional play, but it all depends on tactics.

As others have said, one has to learn tactics. If that is your weakness, focus on learning it.
Blah, blah, blah. Why am I repeating what has already been said ---

Don't give up, work on your tactics, and then choose the opening you like. Maybe d4 Bf4 systems have less tactics, but if you play such openings in order to avoid tactics, you are just hindering yourself.

"In order to overcome your fear, you have to become your fear" (Batman, the Nolan trilogy). I suggest that the players who feels weaker in tactics than in other compartments plays openings when tactics arise in foreseeable patterns (the so-called "thematic" tactics), at least in a good number of cases.
Examples that come to mind are the King's Indian Attack with White (pseudo-sacrifice Nxd5 and e6-push, h4-h5 and kingside attack,...) and the "triangle" Semi-Slav (Noteboom variation, and if White doesn't allow it, the delayed Stonewall) for Black against 1.d4, where tactics arise from the passed-pawn duo on the queenside. Against 1.e4, even some Sicilian variations are not purely tactical and give you some landmarks (Scheveningen, Kan, the Sveshnikov according to Carlsen,...). There are more examples, enough of them to give you a choice according to your tastes.
At very high level (2700+), 1.e4 is actually a quieter approach to the opening than 1.d4. Compare the Berlin Spanish and the Botvinnik Semi-Slav (extreme cases of course), and you'll see why the percentage of draws in 2700+ games is a bit higher with 1.e4 than with 1.d4. Shifting to 1.d4 because it is quieter is not only wrong on a conceptual level, but it is also unrelated to tactics. This being said, I agree with John Watson (the authors of many books, including a repertoire with 1.d4) who claims that playing 1.d4 at some stage (maybe not permanently) is important for the development of a chess player. Again, his point is unrelated to tactics.

I do not buy that Watson statement: Fischer: "1 d4 = dull & drawish".
I knew a player who got good results with all exchange openings: Caro-Kann exchange, French exchange, Ruy Lopez exchange.

play King Indian attack ( KIA)

I think the advice up there in #16 is really good - I might even go one further. Force yourself to play something REALLY tactical, such as the Danish or the King's Gambit. Play a bunch of casual games with it, and analyze your losses carefully. You'll start improving your tactical vision pretty quickly. After that, then yes, find something that suits you. You can't avoid tactics so I'll share the advice I was given: practice what you're bad at.