To use the Samsung Pay on a Gear S3 with a Huawei you need to install the Samsung Wear app and pair with the watch.
When you open the app, you will find a "Payment" option where you can open Sansung Pay. It is very slow, so just tap once and wait till Samsung Pay opens.
It will ask to install some Plugins. Just do it and it will work. (Well, it worked for me with a S3 on my P30 Pro).
As a solution I suggest a duplicate of the SIM card that has not been used with an NFC Samsung payment after.
A duplicate card does not cost expensive, about € 5 and can solve the problem, since there is a link between Service, SIM and the NFC in a Samsung Mobile, I guess for the MST chip.
Please comment on the answer and select as a solution if it worked for you, so that other users of the Community can be aware of it.
Greetings to all
I have a Gear S3 Frontier and use Samsung Pay with it. It has worked with my Pixel 1 and now my Pixel 4. You have to allow for apps outside the play store to be installed for the Samsung pay app to be installed by the Wear app. Then it works. I wish I could do NFC payments with my phone too, but that isn't possible because the full Samsung Pay app isn't compatible. Samsung wants you to buy their phones can you blame them? If they got monthly security updates and timely UI updates like Pixels do, I might have bought one and put up with the crappy One UI software.
I use an HTC U11 with my Gear S3 Frontier and just use Google Pay on the phone and Sumsung Pay on the watch. Google Pay accepts a few more credit cards than Samsung pay and also works with some transport system cards so I think its a better option on the phone.
Swaped from Samsung G S9 to Huawei P30 Pro.
I like two days battery. 70% left in midnight time.
I do enjoy GPAY. Allowed Samsung Watch to unlock device.
Just swipe up and tap. Good to go.
For credit card add use Wearable app.
I DONT PLAN SWAP SMARTWATCH TO SAMSUNG GALAXY.
I perfecf to keep Samsung Gear 3.