Why do you think that chabad has an exclusive on shabbos and Judaism?
I think every frum home has a Jewish calendar with shabbos lighting times and other halachic times that are important for davening, determining ends of fast days, sunset, etc. Many organizations send these out, especially if you donate to them, but you can also buy them in Jewish stores at the beginning of the year. Candle lighting times can be found in these calendars, or in Jewish magazines/ newspapers, or in shul bulletins.
If I need to convert a date, I use whatever site comes up first on google.
I can see how text alerts about candle lighting time can help you plan your erev shabbos earlier in the day, but I don’t see how they will help much close to shabbos or for determining when shabbos is out, when presumably people have turned off their phones. I personally would not remember (or trust my memory if I thought I did) the time shabbos was out if I had seen it the day before on an app. As it is I check the calendar about 3 times as shabbos ends until I remember it correctly!