Drain flies, most of them in a room with no drains

I always had some gnats in my house, but never more than a couple on average day. The last week they have been driving me mad, I'm almost sure they are drain flies (look like a tiny moth, come out at night, jump around more than flying, extreme attraction to light), but I don't get where are they coming from.

I tried to tape all my drains overnight, but they all came up clean, my house has two "and a half" rooms, bathroom, bedroom, kitchen, all connected by a small room in-between, and this small room in the middle is where I'm seeing most of them. Like 20-30 of them on the walls right now, while the rest of the house is mostly empty, while I am moving around the house and turning on lights or screens some of them may spill onto the other rooms, but the bulk of it are there.

This room is like 3 meters by 3, there are no pipes or sinks, I only keep a wardrobe and some tools there, nothing that may be damp or wet. I moved the wardrobe to check if I ever spilled something and I don't remember, but it's all in order, I checked every movable and unmovable surface for larvaes but I can't find anything.

Any tips or ideas to find the culprit and get rid of those little bastards?