Since Hinduism is such vast and full of rich and diverse subject, as a community we need to agree on few on-topics/off-topics hints I guess.
According to Hinduism.SE Help centre below are on-topic Questions here:
- Hindu scripture and mythology.
- Academic questions about Hindu philosophical thought.
- Questions about Hindu practices.
- Historical questions about the evolution of Hinduism.
- Different sects of Hinduism and their beliefs.
Sure, there is no mention of Yoga/Pranayam directly here, and I understand that not everything can be documented to be on-topic in one place. Agree!!
But consider this:
If someone ask question on Hinduism.SE about a specific Pranayam, say, Mann Kumbhak, Rechak and Purak pranayams, and asks more details about the pranayam itself, like how to do it, what benefits etc.
Shall we treat it as on-topic, just because that Pranayam was mentioned in Hindu Scriptures?