The Asus BT8 is a wifi 7 router supported by openWRT and there is quite a few of us running it. I think generally OpenWRT is a good way to go and the Table of Hardware on the OpenWRT site will give you a dizzying array of options for wifi 6 and 7 devices that are supported and you get to pick your spec and price from those available.

You might need the modem device if you are using cable, otherwise its FTTH or DSL then you wont.

If you search for OpenWRT tutorials on youtube you will find a McFly or something like that name and he has a bunch of tutorials on how to set up OpenWRT and a range of more advanced networking topics and how to use OpenWRT to utilise them.