I don't need many ethernet ports so it works for me. My home network speed is less than a gigabit.

It's definitely not for people like OP but may work for other people who don't want to pay much and still have something decent that they can hack themselves.

I have tried to flash open firmware on my router before but it didn't work out. I had a raspberry pi already so I decided to convert it into a router and use it.

A Pi 4 can handle about 1 Gb without issue. It is a great option for consumer workloads at consumer prices. I've certainly seen far worse consumer gear.

The CM4 can hit up to ~3.4 Gbps for one interface over PCI-E, and 4.15 Gbps if you also use the onboard Gigabit interface. Use a 1, 2, or 4-port network card and you can do some interesting things at 1+ Gbps: https://pipci.jeffgeerling.com/#network-cards-nics