Installs just fine but I use Ubuntu Linux. If you are using Windows, try this.

http://randomnerdtutorials.com/installi ... tructions/

Do not change the boards URL in the preferences window. This will not help and might mess up your existing board packages.

I suggest looking at the examples to see what has changed.

One big change is the include file names have changed. Try changing ESP8266WiFi.h to WiFi.h and ESP8266mDNS.h to ESPmDNS.h.

An unofficial port for ESP32 is available. WiFiManger depends on other libraries but there are unofficial ESP32 ports for the dependencies.

https://github.com/tzapu/WiFiManager/issues/241

ArduinoJson Assistant
How to use ArduinoJson?
How to compute the JsonBuffer size?
Paste your JSON in the box and you'll know...

https://bblanchon.github.io/ArduinoJson/assistant/

Generates Arduino code to parse the JSON you paste into the input box.

Alternatively, look at ifttt.com webhooks (previously known as maker channel). Send a trigger using http GET or POST from the ESP. TLS is optional. The HTTPClient library is helpful for this. When IFTTT receives the trigger, it can send email, SMS, tweet, etc.