Help! Almost positive my plant has thrips

A few days ago, I made a post about my Calathea zebrina. It wasn't looking its best and had small holes in the leaves. The consensus was that it was probably nothing, and that might still be the case.

This morning, while tending to my Calathea White Fusion, I saw some small cobwebs under one of the leaves. Then, zooming in with my camera, I saw this tiny, elongated, white bug. I wanna cry.

I have inmediatly put the plant in quarantine.

It's thrips, right?

I live in Europe, and from what I've read (I'm relatively new to plant care), we don't have very strong insecticides here. I've read that potassium soap might work.

Any ideas on how or with what to treat it? Am I doomed?