Might be a little old? Not sure, you would have to research it.
I’m not well versed in what pfSense/opnSense needs, which is why I threw r630s at a project that mattered.
Some cheapo refubed i3 with an Intel NIC card would do. I just suggested the SFF refurb because a lot of people like low power (and SFFs are generally low power)

Theres some that aren’t just money.
There are bots that mirror content from Reddit, just linking to them.
I’ve seen posts that are 3 or 4 crossposts (between community/instances) deep.

I want content.
I don’t want bot content

Having never built an app in .net, my first instinct would be to try to containerise it.
This would make the installation of it (mostly) platform independent, and would let you easily prove it on your development machine.

https://learn.microsoft.com/en-us/dotnet/core/docker/build-container?tabs=windows

Note that docker isn’t the only way. There is also podman, and I’m sure there are others.
All of these build ontop of the Open Container Initiative, and are mostly interchangeable. It’s only once you dig deeper into docker/podman/whatever that you might start running into compatibility issues.
I don’t think I’ve ran into any issues between using docker and podman, albeit for nodejs applications.

My home box ran for a few years with no issues, until I started having DNS issues. I’m fairly certain that was unbound and the blocklists I had selected, tho.
I set up a Cron job to update the block lists every night, and give unbound service a restart.
It’s been solid since then, and my DNS issues have disappeared.

Now, I am checking for updates and installing those every few months. So it gets a restart when that happens.

You could get a refurbished SFF computer that has a low profile PCIe slot, and put an Intel 4 port network card in it.
Would probably cost $150 tops. And its a solid entry! Certainly, that’s what I used before I bought one of the fanless network appliance type things.

My home network has one of those fanless 4 port doodaas from Amazon/eBay if you search for pfSense.
Never had an issue with it, I’m on 300/100mbit broadband tho.

For another project for 10gbps networking, I used a refubed single-socketed dell r630. Probably massively overkill. Also, never saw traffic anywhere near 10gbps… So can’t really comment on that.

I used to use pfSense. It’s great.
I recently moved to opnSense… And I think it’s better.
Both are good, both are BSD, both have similar settings (tutorials are mostly interchangeable)… But opnSense just does it better, updates more frequently, nicer UI etc.

If you are talking to yours ISP, it’s worth getting a bridge modem, and settings details for your own router.
This modem will turn “isp” into ethernet, then your opnSense/pfSense can make the actual connection. This means it gets the public IP directly.

On the “node programming isn’t programming”… I’ve made a lot of money using things like Node-Red and TouchDesigner (seriously, TouchDesigner is the love of my life)

Node-red is amazing.
I have done so many interesting things, strange integrations, quick and dirty glue-code with node-red…

Before I knew about node-red, I bought into some proprietary home automation system (mostly for my boiler and servicing of it). What a mistake.
I wish I could apply node-red to my home.

If I don’t know of a solution to a specific problem, chances are I’m going to use/recommend node-red

Pretty sure it was EA’s “feeling of accomplishment” comment.
https://www.reddit.com/r/StarWarsBattlefront/comments/7cff0b/seriously_i_paid_80_to_have_vader_locked/dppum98/