I got a Protectli one; bit overpriced but they provide instructions to compile Coreboot.

They don't just give you a fish, they teach you to fish, then it's in your hands.

I personally use a router box from teklager.se and they use open source schematics and bios which are actually updated. Without having done a comparison I am assuming they are a more expensive option though. It has been small, silent and stable since I bought it pre-installed with OPNSense though, so I am happy with it.

all software has bugs, most of them get found over time.

no updates, means you are sure to collect known deficiencies.

> Frequency of zero day RCE fixes should not be taken as indication of better security.

true, but lacking an alternative metric, it's at least helpful to gauge the willingness to not ignore problems.