>>105666949
Yeah usually no worries but I'd play it safe with 0.9mm fiber (pic related) and "visible" installation; armored patch-cables can handle almost anything.

A bunch of resources for our German, I'd try to cram a 0.9mm fiber (G.657.A2) into that old Ethernet cable jacket (watch your fingers when cutting it open) and if the bend is too much then I'd go for armored G.657.B2 though it's much thicker and it might not fit inside the Ethernet cable jacket. Not that it matters (armored cables can take a lot of abuse) but with thin 0.9 fiber you could cram as many as you need into that old cable jacket.

https://michael.stapelberg.ch/posts/2020-08-09-fiber-link-home-network/
https://blog.daknob.net/fiber-in-the-home/
https://blog.majid.info/fiber-network/