From what I know it seems the router-oriented designs are mostly fanless, like this[1] semi-random example.

[1]: https://www.aliexpress.com/item/1005004360072281.html

I stand corrected, one is like that thing, no fan The other is a T9 mini PC. It is really small with 2 network ports. It apparently has a fan. I have never heard it. Which is significant to me because I also have some NUCs and those are the only fans in my office and they are annoying in the silence.

Thanks, probably I missed them due to skipping router/multi NIC systems during shopping.