EDIT: I believe I found the answer, it's something turned by this: https://ctatools.com/products/5065
Found some trash on the street that i'd like to take apart, but this screw is in my way.
It's like a hex bolt, but with 5 sides, and rounded (a bit like flower petals).
Here's another picture from the top:
I tried turning it with various tools (hard to get pliars in unfortunately), no success so far. The material is very soft, which doesn't help..
thanks, this might be just the comment I needed! Some of the screws are sunk into a very deep hole (~60mm), so it would be tough to cut a slot into those. But i'll give it a try on one of the more exposed screws, just to see if that gets me anywhere.
Edit again: I was wrong. TIL about EPR Torx. Just search that and you should find the right set.
That's a star bit screw head. Can find it as a torx star or 5-point star bit.
https://www.homedepot.com/p/TITAN-5-Point-Tamper-Resistant-Star-Bit-Set-13-Piece-TIT16137/302134704
People often call variants with other numbers of points "torx" as well. Torx is technically a brand (a trademark) and in that sense, if we were being strict, wouldn't include basically any of the commin TN 6-point driver sets out there, e.g. Wiha and Wera sets. But everyone just says "5 point torx" and so on.
