I have a soft spot for training because a big part of my background is in technical training for adults.
So I'm always enthusiastic about the idea of devs diversifying their income and increasing profitability by offering training services in addition to development work.
Reuven Lerner is the ideal person to teach you about getting started in training because he's done it himself. He's landed recurring training clients, some of which are household tech names. He builds and refines his own curriculum from scratch. He runs a Facebook group for devs who are interested in getting into technical training: https://www.facebook.com/groups/techtraining/
From a profitability perspective, training is very attractive because of how deterministic the pricing can be. Strictly productized services aside, training is priced more like a product than almost any other service I can think of except for services like massages, haircuts, etc. Pricing is usually set on a per student per day basis. For example, you might charge $300 per student per day, and collect $9,000 for a 3-day class with 10 students attending.
Compared to a software project that might just as easily take 9 months to complete as 3, that is highly predictable revenue once the sale is made, and that predictability has a beneficial effect in planning your other revenue-generating activities.