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You can drink a zero sugar saccharine drink every day for the rest of your life and experience no problems from it whatsoever. It’s the most tested artificial sweetener in history and has been used commercially since the 1890s.
People switching to the low and zero sugar products is a good thing. It is much healthier than people drinking sugary beverages - which is the alternative that that they replace. They do not replace water.
Switching from smoking to vaping is an improvement, but not a fair comparison as vaping has been shown to have significant negative health impacts.
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’.