In the patch note of the new update realeasing soon, zeal wrote he will add an in game timer in settings for speedrunning. Will it be used for the run time now?

Only if it uses our retime rules, otherwise no.

The update released today so I checked how the timer works and it starts when you open the keycard door in the opening room so it does not follow the retime rules. I have not checked when it ends.

Maybe add an in-game time variable on top of RTA timing though.

the in game time starts when you open the first door with the keycard and ends when the press the button on the ending submarine

opening first door is actually better for the time starting, the rules should be reconsidered to only use ingame timer since it will be more accurate anyways, its just that maybe recording should start before exiting the sub

Pretty sure that the whole "timer starts when you press the start button" is because back when doors speedruns were popular, it had the exact same mechanic (as far as i remember) but i agree it should be changed, or at least the devs could change the ingame timer to fit with the rules of speedrun submissions

time in the starting room matters too imo