Hello
There is actually some efforts to have Wikipedia and other Wikimedia projects classes online! I'm not sure if I can list all of them, since there are numerous initiatives.
I can cite you a few examples, a lot in French since it i my primary language.
you can find massive open online courses (WikiMOOCs). Arabic and French Wikipedia have theirs. Wikimedia Chile has its own online campus for this purpose (project Wikipuentes). There is a WikiData-MOOC project ongoing.
Live editing sessions, where people are editing and explaining what they do to their audience are also common: French Wikipedia has them on Twitch, so as some Wikidataians, I know a Wiktionarist who hosts them on Youtube.
Commons hosts a lot of videos about editing. Unfortunately, a lot of ressources are dispersed.
As you noticed, all these resources are based on videos. Text-based classes are not really successful.
Some wiki-clubs are also on-line. There are less classes, but it is also a good way to learn how to edit.
Hope this helps!