I start from the OpenWrt devices page. Filter by the Wi-Fi revision I need (ac or ax), opt for 4 cores or more and sufficient RAM, and then read the forum posts and the device page to make a shortlist. Then I look at price and availability.

Pretty happy with my Asus RT-AC68U. I bought it like 8 years ago and they keep putting out firmware updates.

Before that I briefly had a Netgear Nighthawk R7000P and it kept interrupting long-running TCP connections. After much back-and-forth with their useless warranty department, I just returned it to the retailer.

Find a decent embedded system & put Linux on it. I've been using that setup for 20'ish years now & have never regretted it.

See also: pfSense, OpenWrt

I really like my Cudy Wifi routers. They can run upstream openwrt (double check your version). They run some modified openwrt.

They're both cheap and quite good. They're what GL.inet used to be when i last purchased routers before this.

TLDR: Any standard PC with two or more Ethernet interfaces and OpenBSD with PF.

I like the small Qotom Q305p 3205u computers for this, but any small device will do and if you don't care about the router being small and quiet, any form factor PC will work... just need two or more NICs to route packets from one network to the other.