There’s the Teachable, Thinkific, and Podias for great training by some of the more respected and well known leaders, but there are also other places to look for deals on online training.
A few of them might be accessible through your public library. Check their website to see if they have electronic resources. Some of them offer free access to Lynda.com and Safari Online.
In addition there are sites, such as ProgrammingBuddy.club that scope our the latest Udemy courses that are available for free. These can certainly be hit or miss quality wise, but not a bad thing to keep an eye on for some free training to listen to while in your car, etc. Make sure when you follow a link that the offering is still free though, as coupon codes appear to have max limits and run out over time.
Otherwise, even if you don’t see a relevant class for free, most of the Udemy classes run under $20 anyway! Just be sure to read the reviews, see if you can tell how up to date it is, and also check for a preview so you can sample in instructor’s style.
Another option is to check StackSocial.