As part of a project, I was looking for a reasonable CM4, sort of hard to find. Seeed Studios is selling a CM4 on a dual gigabit ethernet carrier board. I got one for the CM4, but decided to test if I could put ipfire on it. Sure enough it works! It runs very hot, so active cooling is required. Without a fan it runs at about 80 C, with a fan it drops down to about 30 to 35 C. I even got the WiFi working on the CM4, but not very well. While the CM4 has 2.4 GHz, 5.0 GHz IEEE 802.11 b/g/n/ac wireless, I could only get it to work in 802.11an, if I remember correctly. I did not explore it very hard on ways to get it to work better.
It is my understanding that DFRobot also offers a dual ethernet carrier board, that is supposed to run much cooler and consume less power. Another possibility is to use the official CM4 carrier board and put a second ethernet card onto the board. I have not tried this yet, but if I do I will report in and let folks know how it goes.