How to setup my Scarlett 2i2?

First, thanks for helping me if you do, or I hope this post will help you if you have the same or similar issues as me. After fighting against the audio problems I had with my Scarlett 2i2 plugged in, I found this page:
Focusrite Scarlett 2i2 working flawlessly on Ubuntu with JACK

It says that the 2i2 3rd gen works perfectly with Jack ! If you’re trying to make your Focusrite work, check this link out. So I did everything I was attempted to do, and I finally had sound ! The reason I’m posting here is that I have a huge latency compared to what I’m supposed to have. JackCtl tells me I’ve got about 70 ms latency, instead of about 4 ms. I can change the settings, of course, and put the latency to 4 ms. What happens then is underruns popping, which are the sign you might have a larger buffer, so a higher latency.

My question is in the title : How am I supposed to configure my Scarlett 2i2 3rd gen through JackCtl so that I have a low latency ?

For the software part, I am using the ALSA drivers with JackCtl. Of course, Alsamixer says me my soundcard doesn’t have any controls. I have got Kubuntu 20.04, with probably the latest versions of everything. I am looking forward for a solution, so don’t be afraid to ask me more information if you need.

Thanks for reading !