A few questions regarding switching from Cable/spectrum to ATT Fiber 2gbps

1. Gateway/Modem

   • Can I opt to use my own modem instead of the mandated AT&T gateway to retain full control over my hardware setup?  No.
   • In case I end up using the AT&T gateway, can its WiFi be completely disabled through the local admin page? Yes
   • Could someone share the technical specifications of the AT&T-provided gateway/modem? There's not exactly a spec sheet.  I can try to answer specific questions.
   • Does it support the latest WiFi standards such as WiFi 6 or WiFi 6E? 6: Yes, 6E: I'm pretty sure not.
     
     

2. Network Configuration and Performance

   • Is it possible to secure a static public IP address? Also, how often does the public IP address change? Yes, for a monthly fee.  The "dynamic" one you get for free can go several years without changing.
   • What are the expected latency and jitter values for the 2 Gbps connection? Depends on your location and the location you're testing latency and jitter to.  My latency for the 500 Mbps is approximately 10 ms to a selection of accessible DNS servers (AT&T's, Google, Cloudflare, etc.)  Jitter is typically low (1 ms or less).
   • Are there any restrictions on port usage? Can I open ports as required for my services? AT&T does implement some port restrictions (found here), including up stream blocking of TCP 25 and source port blocking of UDP 123.
   • Does AT&T employ any traffic shaping or management protocols that could affect the performance of home labs or servers? See previous answer.
     
     

3. Service Details

   • Are there any stipulations restricting the running of public-facing services from a home network?  The agreement is here because you should not take my word for it.  Other than bare resale of the service, I am aware of no restrictions (other than your use should be legal).
   • Does AT&T offer an SLA to guarantee uptime and performance metrics? (thanks spectrum) Not for consumer services.  They do for business services (at an increased fee).
   • Is there a discount available if I decline the AT&T-provided router/modem? No, because you cannot.
     
     

4. Installation

   • What does the installation process entail for the 2 Gbps fiber service? Depending on the current state of your home's access: They may need to run a drop from the port designated for your home to the ingress point of your home.  They may drill a hole through the wall.  They may attach a slack NID as a transition point from drop fiber to indoor fiber.  They will run the fiber from the ingress point to a wall plate near where your Gateway will be installed. (Fishing through walls is not normally something the installer does.)  They will provide a jumper fiber from that wall plate to an SFP connector inserted into a BGW320 combination ONT/Router.  They will configure that ONT for operation on the AT&T network.
   • Is self-installation an option, allowing for network configuration to personal specifications?
     • Upon further investigation, likely not as I don't have their ONT on prem. Without at least a fiber wall plate, it's a no go.
       
       

5. Compatibility with Unifi UDR

   • Are there known compatibility issues with Unifi UDR routers? Not that I'm aware of.  Note the expectation of the Gateway of no more than one IP assigned to a MAC address on its LAN.
   • Can the Unifi UDR router be connected directly to the AT&T Optical Network Terminal (ONT) without the AT&T gateway?  For Internet 2000 consumer service they will install a BGW320 combined Gateway that has the ONT in it, thus: no.
   • What kind of handoff is used for the fiber service, and can it be connected directly to a Unifi UDR router? No.  AT&T Requires use of their gateway.
     
     

6. Support

   • Does AT&T offer a dedicated support channel for users with complex home network setups?  You've already found it.  It's right here.  It's free and worth every penny.  They may offer you a technical support option for a monthly fee.  I suggest you decline it.

As you've asked about Residential/Consumer Fiber service, those are the answers above.  There is a small business fiber offering that is pretty much the same, only you get a different phone number to call and pay more for.  AT&T will run dedicated business fiber (with SLAs, support, equipment and port flexibility, etc. at a greatly increased cost) pretty much anywhere they would run residential fiber to.  

"They will run the fiber from the ingress point to a wall plate near where your Gateway will be installed. (Fishing through walls is not normally something the installer does.)"

All of the pictures I've seen of Fiber Jacks (and ONT Service boxes as well) shows the device mounted on drywall with no sign at all of the incoming fiber cable, just the cable-to-gateway coming out.  So the incoming fiber cable must be coming in from behind, through the wall.  How is this possible without fishing?  Do most installations have the fiber cable running along the wall to the jack, despite what the pictures show?

Drill through an outside wall and mount the wall jack on the wall opposite the drilled hole. If a brick home, drill through the mortar between the bricks. 

☝🏻☝🏻☝🏻. Can confirm

OK.  So essentially, the fiber jack location is restricted to being on the outside wall of the room.

No. It’s up to the tech to decide. Make it easy for the tech and they can put it somewhere else. Such as  run conduit to a networking closet. Techs are on a time standard so they want to get the job done quickly without getting dinged for taking too long. a new install is probably allotted 3-4 hours. 

Hopefully, a fiber jack can be installed in a networking closet without coming through a wall from behind.

Cable typically permits bridging a modem as you know, and which you can purchase and furnish on your own.  Att does not.  The best you can do is use IP passthrough, which is not a full bypass.  Whether or not this is satisfactory is something for you to determine. 

"Hopefully, a fiber jack can be installed in a networking closet without coming through a wall from behind."

Tech arrived today and installed internet fiber upgrade.  In the wiring closet, he mounted the fiber jack on top of a white plastic adapter that allowed the fiber cable to enter from the side, not from behind the wall.