There are many meditation courses available online but all of them make claims about their techniques, the efficacy of which we cannot verify independently from other sources. They could as well be placebo! I am looking for reliable courses/exercises that are proven to have positive benefits.
The positive benefits could be include any positive benefit (ranging from something like better clarity of thinking to something like better digestion). I am keeping the definition of "positive benefit" open to interpretation so that we can get a variety of responses under this thread.
I will suggest few very basic and easy "exercises" of Yoga that have long-term benefits. But Yoga has to go hand-in-hand with dietary discipline. And as they say, good things take time. This is very true with Yoga. It is not a quick-fix type of solution.
So, here are the exercises, they are collectively called as "Praaṇaayam". These are breathing and gut exercises:
https://www.wikihow.com/Do-Pranayam
https://www.youtube.com/watch?v=pYu6V0PxIyU
https://www.youtube.com/watch?v=qcQW1P6Y7AA
Do these exercises 10-15 mins every day early in the morning and before going to bed. Try to sleep early and wake up early. And have fresh(home cooked) "light and easy" diet as much as possible.
Following these principles will help with general health benefits. It will take some time to see the results of this.
By the way, a lot of serious folks hang out on r/streamentry, and you may be better off asking there. They're a thoughtful, welcoming, and kind community as a whole.
I'm going to be taking this course in January. It's an online, 3-day course on tummo. There will be a followup in August. https://ligmincha.pl/event/kurs-tummo-styczen/
Incidentally if you're anywhere near NY, I'm trying to put together a tummo practice group in Brooklyn, and you're welcome to join.