I don't get what all you are asking. But part of the answer is:
Big companies geoblock all the time.
Countries where the government does not like unreviewed content, the same occurs.
To my knowledge, Britain does not geoblock every IP from Brazil. Try this to test:
Google
The other possibility is that the podcast company's version of antimalware is blocking a part of the IP range you are in.
Brazil is not blacklisted on the datasets we have. Your ISP may be. And you may be dealing in the UK with a company or its subsidiary that just got a new blacklist. And, your ISP is on it.
'Underground' has a negative side:
FWIW: A lot of security people are trying to learn how to deal with 'underground' or dark net services like tor.
Unless you are really security savvy, messing around in a lot of dark net sites may get your system irreversibly trashed. So say the security guys at my company.
Instead of doing something counterproductive, see if you can find a way to email the podcast site owner, in order to see if s/he can help some way.