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Simple question but can be a complex answer. Basically it depends where your phone gets DNS from: if it’s using the ISP DNS (or some other public DNS server) it will resolve the public internet IP of your server and the data will route out to the ISP WAN before being routed back in.
On the other hand you can configure a split DNS system, so say you are using your modem/gateway as your DNS server and it forwards DNS queries up to your ISP (or other) DNS server - a common setup, 1. you can add in a static host entry for your local server. Eg ‘yourservice.yourserverdomain.com = 192.168.1.20 (your server’s LAN IP)’
Now when your phone is on the WiFi and it looks up your server’s address it gets the local IP and routes locally, which will be faster.
If you need more info, search for terms like ‘reverse proxy split DNS best practice’.
I’m quite certain that this deal is intended to be unpalatable to Ukraine - it was cooked up by Trump and Putin after all.
Either way they win:
Ukraine takes the deal: they win; Ukraine says the deal is ridiculous and walks away: then Russia & Trump brand them as unrealistic agitants and delay for more favourable terms and extend the war.