for local providers / MVNOs, you can generally find out easily the network, but as you noticed supporting remote/easy eSIM purchase (or needing KYC/passport scans) is very inconsistent.

https://www.reddit.com/r/GreeceTrave...efore_leaving/
this report says need in person KYC. some countries allow online KYC (selfie of passport etc) but not Greece?


for non-local roaming/travel eSIMs, i'd say that 60% of them do NOT tell you the underlying network provider, or the exit IP (extra latency/delay in loading pages). majority don't need KYC but I know a few that do

do you truely need unlimited or more than 3GB/day?

roaming/travel eSIMs will be expensive for that (at least $1/GB, or if you commit to connectpls or Orange holiday/ESIM.net with phone number - 100GB for $40-$60, which is $0.3-$0.5/GB). and if you choose correctly, these roaming/travel eSIMs may support multiple provider (and having a Europe exit IP would minimize latency issues), and more useful if traveling across Europe.

local providers usually is cheaper? ($10-$20 for large data bucket) and su pport some Europe roaming (typically up to 23GB max, usually less)