I believe similar was mentioned in an older post but one of the free online courses you can take for Skywarn spotter classes is available with NWS on UCAR Comet MetEd
https://www.meted.ucar.edu/training_course.php?id=23 (along with tons of other cool weather and weather tool training on there).
It does mention your local NWS office may still require a face to face class to be certified and to contact them to see what they require. Mine emailed me automatically within a week of taking just the online course, filled out my contact info on a form, and was officially a spotter right after!