How to make a hotspot with a popup window (advertising and Use Internet button)?

Question

WiFi

Good afternoon. Need your advice.
Needed:
wifi in a store where, when connected to an open network, a popup page popped up (a sudden authorization page, like in all coffee shops).
The popup page should have an advertisement (a page that can be edited) and a button for accessing the Internet without authorization. After pressing it, a person enters the open spaces. If there is an option through liking the group on facebook, I will be very grateful.
The need for a popup is simple - everyone uses mobile phones and does not use a browser. It was possible to make a redirect through the browser, but I can’t understand how popup works. Who and at what level is responsible for this is not clear.
Available:
ubuntu server (LAMP, iptables)
d-link dir-300 with dd-wrt firmware
or
hostap (wlan2)
I tried wifidog myself and I regret it, because it is a forgotten old one from which I did not achieve the desired result (wifidog auth+wifidog gateway). And plus an attempt to tie wifidog authpuppy - I thought it would save me, but it was not possible to install it.
I've been surfing the Internet for 2 weeks now and I can't find anything other than Mikrotik. Please help - there is no opportunity to buy other equipment.

Answer 1

CaptivePortal - I answer like all the dozens of people who have already raised this question here, master the search.