Deepbluehum, I am very happy to hear about your extensive background, and the high quality teachers you have been able to connect to. I don't think anyone here was conflating kundalini with tummo, aside from the OP who was merely asking if there was a relation.
But I don't believe it is outside the scope of Vajrayana yogas, and for some example / context of Vajrayana master's references to kundalini-- this is Lama Yeshe:
Among the realizations...many people are interested in tantra realizations, very high tantra realizations like Six Yogas of Naropa, chakra, wind meditations, generating heat in the body from tummo meditation, so forth, kundalini, the bliss, the kundalini bringing up and down, which even Hindus can do that. So nothing particular. Without compassion these things can become cause, not only cause of samsara, but even the cause of the lower realms if it’s done with attachment clinging to this life. So without the motivation of compassion even one do get some experiences, some powerful experience of those in the section of the graduated completion path but without compassion it becomes nothing special.
So it’s like, [pause] Tibetans always use the example this cheese, the dry cheese with lots of butter, so real taste is from the butter. What makes ice cream delicious is by what, cream or by sweet? [Student: Both.] Anyway, whatever makes the ice cream delicious. So, without that. Or like cake, something, butter and those sweet, whatever it is, that makes flavor, interesting the flavor, so like that. So the compassion makes everything worthwhile and rich, all those experiences rich, meaningful, cause of enlightenment. It protects you, yeah, protects you falling into the lower nirvana, falling, become cause of reincarnating in samsara again and even particular the lower realms.
Also, as I mentioned last time, I gave a few examples how this is the answer for everything, all the problems that one has in the life, I said bodhicitta, good heart, is the solution for everything.
Another excerpt from Lama Yeshe:
Lama.Yeshe:Control of kundalini energy (=libido, sexual energy, naga energy) is important even in ordinary orgasm. You cannot have a perfect orgasm if you cannot control your energy. It is the same in tantra. You cannot experience perfect bliss if you cannot control your energy. The fact is that if we lose our energy, we have to energy to utilize. In order to use energy, we need energy. If we don't have it, we cannot use it. This is logical, and you can see it clearly from your own experience. When you concentrate well and control your energy, you can experience more bliss, which you then unify with the wisdom of nonduality.
If kundalini starts to flow uncontrollably during your meditation and you begin to experience orgasm, try as much as possible to hold it and have it expand inside the secret chakra. Try to hold the energy there as long as possible. The longer you can hold it, the more pleasure you will experience and the more possibility you will have of utilizing that pleasure by unifying it with the universal reality of nonduality. In this way, you learn to control your body as well as your mind.
So here we see that Lama Yeshe was very familiar with kundalini energy, he differentiated working with it from tummo practice, acknowledged that Hindu yogis utilize it too, but clearly in the last quote we see that he deems it something innate to the body which is important to learn to work with for a yogin regardless. The main thing, is motivation. This is from Lama Yeshe. I am not agreeing or disagreeing with him. Just providing references.
Similarly, here is an excerpt of a question and answer session with Chogyam Trungpa:
Student: Rinpoche, could you tell us how guna is connected with spaciousness and how all that is connected with the chakras?
Vidyadhara: Guna, well guna is another type of intelligence, seems to be. It is similar to the intelligence or the feeling of earth, at the beginning, because guna is connected with earth as well as space. The color is yellow, a gold color. In other words, in regard to the sharpness of the chitta and the intelligence--in order not to get carried away with the excitement of the intelligence, guna brings it down, regulates the whole thing together, and then transfers its process to action, or karma. So guna, in this case, acts as a scale. It has all the qualities of the other elements. It has the intelligence as well as the particular qualities of sanity.
According th the yoga tradition as well, in the visualization of the chandali and in kundalini practice, when the chandali flame is raised up in the navel chakra, that's the most dangerous time because it's the junction of all the nadis. It's the most dangerous point, how to relate to it. So one must develop guna in this case to even out and work with everything in a very even principle, because there's the likelihood of losing ground.
Guna is the space quality. In other words, guna is the space of earth itself. It is not space space, which is the intelligence in this case, but the space of earth. Guna is the regulator which evens out and balances the whole situation. It seems to be quite dangerous, this process of working with energy, like chandali practice. You're playing with energy. If you don't work properly with the guna principle, then there's the possibility of distorting all the nadi systems into imperfection. So guna is, therefore, space---space which fills every gap, space which divides the relationship of this to that, like the space in our everyday life. There are a lot of things that we could go into details about, but we don't seem to have enough time.
I won't go deeply into this but let's just say that I have received personal advice regarding my background in Kundalini from different luminaries of the Dzogchen tradition and it was never treated as something outside of the tradition, as separate.. in the same way that the masters above refer to it casually within the context of their yoga teachings. However, it is not understood in any way to be the end-all-be-all as it is referred to in Hindu yoga traditions of kundalini yoga. It is merely another aspect of the inherent energies of the body, and it is part of the map of relationality. It is important to see it in the context of proper view and motivation, especially if Dzogchen is the larger field of one's practice, which is very different than the context of yogic traditions where kundalini is contextualized in a more supreme manner.