Comment by bjackman
5 hours ago
I'm a Brit living abroad, when I visit the UK I use a Tailscale network with an exit node at my home, and yeah this always seems to work for me.
Going the other way around to try and watch British TV I used to find with a normal hosted VPN services could still figure out I wasn't in the country, but now I have a Tailscale exit node at my mum's place in the UK it always works fine.
So I suspect it all comes down to the IP source, probably a residential IP is the best possible case and with commercial VPNs it depends on how hard they work on isolating their IP blocks from known datacentres.
Apps can read sim card info. Its country and whether the card is currently in roaming, you can't full them that way
You would need to get your sim card out of your phone and use wifi or buy one of them foreign esim
For vpns I actually found that websites that block vpns for some reasons are worse at detecting commercial vpns than when you deploy your own on vps
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Also I forgot about other things. When my phone for some unknown reason had its region set as GB, I had British ads in YouTube music
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Commercial VPNs publish their exit nodes IPs online. There are services like ipinfo.io which can accurately determine if you are using a known VPN service.