I've been running Untangle for a few years now. I run it on one of these right now and have had no issues. Get line rate across L2 VLAN tagged subinterfaces as well as full speed on my 800/15 Comcast connection.
here is the link https://www.amazon.com/dp/B0B287Q7KG?ref=ppx_yo2ov_dt_b_product_details&th=1
this one has realtek
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then i also tired with a brand new Minisforum UM250 Mini PC that has intel chipset both same problem i also have tired many deferent cables aswell
If you have an old computer you can repurpose, Untangle is a great option.
I spent $50 on this Quad NIC. https://www.amazon.com/gp/product/B074C5DHS3/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I also got a SSD (480GB or 500GB can't remember ) for about $50.
Finally, I went with Untangle's Home Protect Basic which is just $50 a year.
Since I was able to repurpose an old computer and only need to buy the NIC and an SSD, I got the whole thing running for like $100 (plus tax) and $50/year for the subscription.
If you really want Live Support, you have to go with Home Protect Plus at $150/year but I've never needed it.
I also added a Raspberry Pi running PiHole and Unbound into the mix pretty cheaply as well.