Thanks for verifying the site works for you, with Opera. With that bit of information, I continued to work on another possibility, and that is, there may be an incompatibility in the selection of Extensions installed on this copy of Opera.
I clicked 'Disable' on all of them and tried transfer.pw again.
Now it works normally, for the first time!
I'll have to bring the extensions back again, one by one, and see which is'killing'that web site.
Thanks also for letting me know there is a more recent version of Opera. I wouldn't have suspected that, with About Opera reporting 'your system is up to date' -- when that's not the case. Also, Synaptic fails to show there's a version 46.x.
If we may off topic a bit, which repo is giving you 46.x? Obviously, the ones I'm using don't have it.