Browser / Version: Firefox 82.0
Operating System: Windows 10
Tested Another Browser: No
Problem type: Site is not usable
Description: Browser unsupported
Steps to Reproduce:
Page is here: https://www.amazonfutureengineer.fr/programmes/cyber-robotics-challenge
Only Chrome is supported claims Amazon (first FAQ)
Not a bug as such but I have been seeing, in the last few months, a lot of websites or apps which are only compatible with Chrome. Really reminds me of 15 years ago with Internet Explorer, when Firefox has a tiny market share so very few people cared about testing on it. Lazy developers and companies which try to save money on development and only test on Chrome. No doubt there will be more and more of this in the near future, meaning that 'alternative' web browsers or with a smaller market share will be indirectly pushed out of the market.
I am surprised that Mozilla, for example, doesn't take this more seriously. Focusing on privacy is great but this is not how they will survive. Future doesn't look bright, especially since Microsoft is using Chromium.
Browser Configuration
_From webcompat.com with 鉂わ笍_
Thanks for the report, I was able to reproduce the issue. Expanding the first question from "FAQ" displays the message.

Tested with:
Browser / Version: Firefox Nightly 84.0a1 (2020-11-15)
Operating System: Windows 10 Pro
Moving to Needsdiagnosis for further investigation.
I sent them an email.
I am surprised that Mozilla, for example, doesn't take this more seriously. Focusing on privacy is great but this is not how they will survive.
Hey anonymous reporter; thanks for you concerns. Rest assured that we take this very seriously, which you may notice by the fact that you actually have the ability to report such issues, and that you get responses and actions from Mozilla employees within 48 hours - even though everyone was enjoying their weekend. :)
Unfortunately, everyone has resource constraints and everyone has to make decisions what to do and what not to do. Sometimes, these decisions are harder than one might imagine. We, as in Mozilla, can't just aggressively override the User Agent string in such cases, especially if we don't have the ability (and, quite frankly, resources) to 100% test everything here - so in the worst case, we do the UA override and break things even more.
In cases where we can't easily judge the scope of an issue, like it is the case here, we usually default to reaching out to the site first. That's what I have just been doing. Sometimes, this outreach results in a site being fixed, or in us learning about a Firefox issue that's actually blocking the rollout. I know this whole thing can be frustrating, because there is no way for us to simply make it work(tm), but that's the world we're in.
If you want to help, you can do your part as well: keep reporting those cases, and also do reach out to the site itself. Try to find contact information, or open a support ticket, and say that you'd be really interested in using Firefox. I'm not advocating for starting spam-campaigns and convince thousands of people to spam Amazon, but if you need to have access to the contents and Firefox is your main browser, then I think you should make your voice be heard. :)
Most helpful comment
I sent them an email.
Hey anonymous reporter; thanks for you concerns. Rest assured that we take this very seriously, which you may notice by the fact that you actually have the ability to report such issues, and that you get responses and actions from Mozilla employees within 48 hours - even though everyone was enjoying their weekend. :)
Unfortunately, everyone has resource constraints and everyone has to make decisions what to do and what not to do. Sometimes, these decisions are harder than one might imagine. We, as in Mozilla, can't just aggressively override the User Agent string in such cases, especially if we don't have the ability (and, quite frankly, resources) to 100% test everything here - so in the worst case, we do the UA override and break things even more.
In cases where we can't easily judge the scope of an issue, like it is the case here, we usually default to reaching out to the site first. That's what I have just been doing. Sometimes, this outreach results in a site being fixed, or in us learning about a Firefox issue that's actually blocking the rollout. I know this whole thing can be frustrating, because there is no way for us to simply make it work(tm), but that's the world we're in.
If you want to help, you can do your part as well: keep reporting those cases, and also do reach out to the site itself. Try to find contact information, or open a support ticket, and say that you'd be really interested in using Firefox. I'm not advocating for starting spam-campaigns and convince thousands of people to spam Amazon, but if you need to have access to the contents and Firefox is your main browser, then I think you should make your voice be heard. :)