Managed to get the code. Here is what I did (pure trial & error after several frustrating attempts). the instructions may not be accurate. I've tried my best to remember and type. I hope it helps.
I used Chrome browser in my Flip4 instead of Samsung Internet. Wherever applicable, I had to accept the annoying privacy prompts & cookies.
- Opened Chrome browser, navigated to Samsung.com UK site and Signed in to my Samsung account
- Navigated to https://www.samsung.com/uk/boost/, then to the Disney Plus boost offer section and clicked Redeem Now . There was a sign-in link and signed in again. Wherever you see sign-in, just do it to avoid doubts. You'll see the claim code displayed.
There is another annoying thing I found. It says I need to redeem by 14th Oct 2022 & not 30th November 2022. However, the screenshot of the offer page shows 30th Nov 2022 & also in FAQ below says claim by 30th Sept 2022 & redeem by 30th November 2022.
I guess you meant Samsung Boost app, not members app.