Is it okay to use a cracked launcher for speedrunning like TLlauncher which provides no benefit to the gameplay and is the same as the official launcher?

ask the forum of whatever game you're asking about.

the answer to this question is in the rules and the faq, and there are several threads in the forum about it.

cracked launchers are not allowed

I remember one of the MC mods saying that they don’t really have a way of knowing if you’re using a cracked launcher, supposedly the gameplay (at least in singleplayer) is the same. Although that doesn’t mean it’s morally right to use a cracked launcher, buy the games/software you use.

Most cracked launchers are banned because they modify the game in some ways, but they can't recommend a specific cracked launcher to use because they are illegal.