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.
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