This is a great example... except I think the right answer to "what exactly would you do in this case?" doesn't support your argument.

I'd document that mobile Opera with Javascript disabled is an unsupported config, and ask a team to make a help center doc asking mobile Opera users to enable JS.

This is too logical, practical, and pragmatic. Which product owner/project manager would approve such a thing!?

Being able to think of simple, practical solutions like this is one of the hardest skills to develop as a team, IMO. Not everything needs to be perfect and not everything needs a product-level fix. Sometimes a "here's the workaround" is good enough and if enough people complain or your metrics show use friction in some journey, then prioritize the fix.

GP's example is so niche that it isn't worth fixing without evidence that the impact is significant.