We have an extensive resource, the 10 Gig Networking Primer, that discusses the best cards.
This is a discussion of high speed networking for newcomers, with specific emphasis on practical small- to medium-scale deployments for home labs or small office users. It originated with a forum thread located here that has many pages of...
www.truenas.com
It's important to note a bunch of things:
1) 10GBase/T is a HORRIBLE technology and you should avoid it if you can
2) That's not an Intel X540 card. It may claim to be, but the images are clearly not. It may be some vendor's private label version that uses Intel silicon, in which case it might work fine. But there is a huge trade in both knockoff X540's that "look like Intel" cards, and also cheap clones (which is what I suspect could be the case here) that use back-alley Shenzhen silicon.
3) Most of those come from Asia. Two different warning flags here, one is that these claim to be distributed in "Walnut, CA" which is the Bay Area, a common source point for fraudulent knockoffs, and the other is that the name of the seller contains "au" as though they're trying to claim Australian nexus (which is sorta something you see on fraudy vendors on ebay.au). On the other hand, if you pull up the member's page, they do cop to being in China, and registered on eBay since 2018 with a very good feedback rating, but a relatively unremarkable number of feedbacks. Also they have what appears to be a wide selection of networking products.
Beware the seller who has a name like shiningrainbow2021 and is selling x520 cards alongside sandals, electric foot massagers, and fashionable purses is a questionable seller who may be getting knockoff crap shipped from Asia by the containerful. They will have usually very positive feedback figures in like the five or six digits. (link goes to a post with more detail). Your vendor here does not appear to fall into this category, so that's at least positive.
Also good advice for eBay here.
So. You could end up with a card that actually has Intel silicon (or knockoff clone that works 100%), but even if it does, be aware that 10GBase-T is a horrible copper technology, and that if you can, SFP+ and fiber is a better choice, it's lower latency, lower power, and much less twitchy. Also, if you are using this for a virtualized FreeNAS under ESXi, do note that ESXi is very picky about the cards it will work with.
