Ubidots for iSpindel
Ubidots vs Ubitdot STEM
Here is a link to a Ubidots article laying out the differences between the free and paid version of Ubidots.
Unlimited Ubidots 30-Day Trials
I found as of July 2020, you can sign up to the Ubidots full-featured 30-day trial multiple times from the same device provided that you create a new account using Chrome’s incognito mode (or similar mode in different browsers). Ubidots currently doesn’t validate your email address, so you can put a fake email address in without issue, just don’t lose your password as you won’t be able to recover it. To sign up you’ll need a unique username, app name, and password.