How can I completely and permanently remove the ability to access the internet from a Debian derivative?

The machine will be a laptop.

So let's say I'm doing this on Antix Linux or MX-Linux, which are both based on Debian. I already set up everything that I want. Now I wish to make that installation incapable of accessing the internet ever again -- even if I want it to. However, I wouldn't want to achieve that in a way that will negatively affect any application I might need. How can I do that?

You may be curious about my motivation. It is simple: that machine should be only for writing and nothing more. Maybe I'll use YLINAT, @Areldyb's Timasomo project.

For the purposes of my usage, it is nothing more than an electronic typewriter with a screen. That is a drastic measure but I have ADHD and I need to write. I'm afraid that if I don't do something about it I'll see myself in a difficult situation regarding deadlines. I'll just take the laptop with me to a quiet place and leave the cell phone at home.

Every day I will take my writing off the laptop via USB and back it up.