Never. The only time it hapens is if I'm trying to access something not approved in my work pc. In my home never. But Iran is in "the list" so yeah you'll probably have trouble even paying for vpn, but you can get some free options to bypass that
I rarely see it but it happens every now and then. And I sometimes get paywalls or videos are georestricted. And some websites don't want to implement the GDPR and refuse service to european users.
And Project Gutenberg (the book archive) had been blocked in germany for years.
Legal issues. I think they got sued and geoblocked the whole country for years. We don't have the same concept of 'public domain' here. I think it's 70 years after the death of the author here. And Project Gutenberg uploads books way earlier since it's a fixed (and shorter) amount of years after first publication in the USA.
I live in the US and sometimes German music on YouTube is blocked from my region because of their licensing laws, but it isn’t something I encounter often.
I've actually encountered it a couple of times trying to access some Israeli sites. More specifically I've encountered it in Hareetz for sure and I think it was after I disabled the clearURLs extension that it was fixed. And another site that I still cannot access is the Israeli post. I've managed to access it after turning on VPN and trying a couple different locations, but it gives me this 403 error whenever I try to open it w/o VPN. And also on the same site, my antivirus has warned me about a JS/Agent.PIV threat a couple of times that I've tried to open it, not every time, but it has happened multiple times, as I've had to track an order for some days.