@Narya so. your home network can’t be seen for outside your home unless you do some extra work

configure your router to allow incoming requests(off by default)

so, let’s say u want users outside your house to use a url like

http://fribble.home.someplace.com:8023

then your router has to pass that request only the machine on your network running MagicMirror on port 8080

this is called port forwarding

now the next challenge is to locate your router on the internet, as connected by your isp.

by default the isps give out addresses via DHCP , and do not register a name for each home/router.
you can find the address using the
https://www.hashemian.com/whoami/
url on your machine running MagicMirror
you can use the ip in your qr, http:ip_address:8023

now. ‘most’ of the time your router will retain one IP address. but it CAN abd DOES change

there are services that can map a fixed name to an isp IP address.
I use dyndns.org, and my router keeps the setting up to date. ( a Google search will find other ddns services)

then your qr code would use the fixed name and port used in the port mapping.

now, SOME isps don’t allow incoming requests on normal accounts. I’ve had two over the last 20 years that required a special static address account ( for more money)

where would u post your qr for them to use from their phone?