Sure you can control just about anything by using the correct software on a publically accessible computer. For a Raspberry and a light it might just a 120vac relay board connected to a gpio pin.
http://www.instructables.com/id/Simple-and-intuitive-web-interface-for-your-Raspbe/

Just remember, the S in IoT is for security.

https://arstechnica.com/information...in-the-world-by-exploiting-this-smart-device/

This event brings to mind the worn-out cliché that the S in IoT—short for the umbrella term Internet of Things—stands for security. While many IoT devices provide convenience, a frightening number of them are designed with minimal security protections. Outdated firmware with known vulnerabilities and the inability to update are typical, as are myriad flaws such as hardcoded credentials, authorization bypasses, and faulty authentication verification.

What's changed? Not much.

 

Haven’t tried this, but it might work. Have the Pi send you an email and extract it’s IP address from the email header.

 

I haven't used Dyndns for a while, but in the past I used it to remotely manage the p2p and torrent clients on my home PC. You'd also need to configure your router to open up ports and stuff. Or, you should be able set up a scheduled batch file which would dump the network status to a text file then email it to you.

Running Tasmota on your IOT devices frees you from the need to rely on servers out in the cloud. The Tasmota device has its own little web server where you can turn it on and off and configure it, and it can be configured to emulate other things like Philips Hue or Belkin Wemo, which can help with integrating it with smart speakers.

Many of the current production IOT things have gone to cheaper chips that aren't compatible with Tasmota, but older stuff is showing up at bargain prices. There were Woods WION Wifi switches at Dollarama yesterday, and another place had a bunch of Merkury/Geeni RGBW WiFi LED strips. I didn't bother with the WiOn switches since I already have too many 120V switches (and it's unnecessarily large), but the TYWE3S brain in the Geeni sells for $8 on Aliexpress, so getting it complete with driver and 2 m of silicone-coated RGB-WW-CW LED strip is hard to resist.