Xfinity Internet Upload Speed Capped at 40 Mbps. Should be > 200 Mbps as part of 2000/300 internet Plan.

This looks like a common issue but not sure why Xfinity support team didn't provide a generic solution/guideline.

Similar issues I googled and read through: 

https://forums.xfinity.com/conversations/your-home-network/upload-at-40-mbps-with-gigabit-x2-and-arris-s34/66e4c823a6879c6c7ca4cb19
https://forums.xfinity.com/conversations/your-home-network/upload-speed-being-throttled-from-200mbps-to-40mbps/660656ade5bf876df6460c12
https://forums.xfinity.com/conversations/your-home-network/issues-with-upload-speeds-dropping-from-300-mbps-to-40-mbps/66d07ab8ca97cc59af69b5d4
https://forums.xfinity.com/conversations/customer-service/not-getting-comcasts-new-200mbps-upload-speeds-support-edited/63f4698542546f76d9f3059b

Last week, I upgraded my internet plan to Gig X2 (2000/300) from Gig Extra (1200/200). I realized that my previous modem (Netgear CM1200) won't let me get the full speed I pay for, so I went to Xfinity website list to get a compatible new modem -> Netgear CM2000. After activation, it turned out the download speed is ranged from 1000 to 2000 mbps (depending on the testing website), however, the upload speed was capped on 40 mbps. I switched back to the old modem, the download speed was 9xx mbps which was expected, but again the upload speed was 40 mbps. I then googled a little bit and figured out that Netgear CM2000 is not in the current "recommended" list: https://assets.xfinity.com/assets/dotcom/projects/cix-4997_compatible-devices/2024.06.26%20Full%20List%20of%20Compatible%20Devices.pdf. Based on what this "Next Gen Speed Tier list" says, I bought CODA56. Based on the various sources: Amazon customer reviews, Xfinity forums, and Reddit, it sounds like CODA56 would be a solution. However, it didn't work for me after the activation this morning. I tried restart the modem, router several times, nothing worked. 

Note: I'm using a cat 7 cable between CODA56 and my x86 router (2.5g). And all the speed tests were made on the x86 router directly through "Speedtest by Ookla. which is the official command line client for testing the speed and performance by Ookla". 

Here're some testing results running through different modems

https://www.speedtest.net/result/c/55600fb1-f015-4ea6-abb7-f72a7556ca58

https://www.speedtest.net/result/c/138c0c53-b309-450e-af50-27e2f769ab24

https://www.speedtest.net/result/c/128e8f6d-24fe-4238-9bef-847a6ad18901

https://www.speedtest.net/result/c/77fdd363-ca0b-4404-8152-35b9efecbdde

https://www.speedtest.net/result/c/cb9f1bdd-337f-4626-a3ea-8262f724e5af

Here's the exp I had to make things

• I have called Xfinity support several times in the past few days. Even though I'm an IT guy, performed all the necessary troubleshooting steps before the call, and clearly knew what I need, the Xfinity voice assistant is just like .... (you know that). The current voice assistant is making customer experience even worse. A suggestion here is if a call is from same customer and same phone #, at least please refer to the recent call histories/recordings in Xfinity system to save customer some time.
• After struggling to get the live agents, the agents asked me to reset/reboot my modem many times and they ran diagnoses every time I called in, but nothing worked.  One of the online live agents also helped to schedule a technician appointment without telling me I would be charged for 100$ for "professional installation". Well, technically, I've installed the device and service was up and running, it just didn't meet the agreement for what I pay for. I had to cancel the appointment just now to avoid this extra charge. 
• I also went to Xfinity store and they told me they can't help if the modem is 3rd party but xFi could be a solution, but you need a new plan/addon (obviously this is a bad strategy for promoting xFi to your customer for 180$-300$/year).

Finally, I decided to post here for a last try.