Notions of something and nothing also depend on appearances, not the other way around. So appearances are freed from the proliferations "something" and "nothing".

As to the exact way that appearances appear, this is just dependent arising. But since nothing is established by dependent arising we don't need to ask where it comes from. We don't need to ask 'how could something come from nothing?', because no 'something' is ultimately established. What is 'established' is nothing but an illusory appearance.

Those appearances do follow relative rules, in the same way that inside the story world of harry potter there are relative rules about how, for example, spells are cast (say a magic word, wave the wand a certain way lol). The world of Harry Potter is not ultimately established, and yet what appears in that world has self-consistency and relative validity to the other appearances in that world. All appearances are like this. Clearly apparent, but illusory, dreamlike, without substance, not truly established. Yet like a story book what appears still follows rules which are conventionally valid.

An ultimate background substratum or source behind appearance is precisely the illusion seen through in anatta realization, only vivid radiant appearance itself knows and rolls without a knower. Without that insight, one does not go beyond I AM or at most substantialist nondual realization.

As described in my own article https://www.awakeningtoreality.com/.../different-degress...

Mind is skin, flesh, bones and marrow. Mind is taking up a flower and smiling. There is having mind and having no mind... Blue, yellow, red, and white are mind. Long, short, square, and round are mind. The coming and going of birth and death are mind. Year, month, day, and hour are mind. The coming and going of birth and death are mind. Water, foam, splash, and flame are mind. Spring flowers and autumn moon are mind. All things that arise and fall away are mind.

----

Dogen:

‘Mind as mountains, rivers, and the earth is nothing other than mountains, rivers, and the earth. There are no additional waves or surf, no wind or smoke. Mind as the sun, the moon, and the stars is nothing other than the sun, the moon, and the stars.’

----

“For Dōgen, Buddha-nature or Busshō (佛性) is the nature of reality and all Being. In the Shōbōgenzō, Dōgen writes that “whole-being (Existence itself) is the Buddha-nature” and that even inanimate things (grass, trees, etc.) are an expression of Buddha-nature. He rejected any view that saw Buddha-nature as a permanent, substantial inner self or ground. Dōgen held that Buddha-nature was “vast emptiness”, “the world of becoming” and that “impermanence is in itself Buddha-nature”.[23] According to Dōgen: Therefore, the very impermanency of grass and tree, thicket and forest is the Buddha nature. The very impermanency of men and things, body and mind, is the Buddha nature. Nature and lands, mountains and rivers, are impermanent because they are the Buddha nature. Supreme and complete enlightenment, because it is impermanent, is the Buddha nature.[24] https://en.wikipedia.org/wiki/Dōgen#Buddha-nature“

If you want a simple answer, this presencing-appearance rolls on via dependent origination without an agent, nor an ultimate source, nor a background.. without beginning and end. No beginning, and definitely no ultimate beginning or origin either, and if you wanna get a little intellectual, we can say, Buddhists have no problem with the infinite regression of beginningless dependent origination on a relative level -- infinite regression is not a problem or illogical to us, instead the whole 'uncaused Cause' is itself illogical to us (if everything must originate from a creator source, why doesn't that logic also apply to the creator?). There is simply no starting point from which this 'the whole thing started'. With insight it is so clearly seen that there is only ever luminous manifestation, there is no such thing as an 'unmanifest source', and no such thing as some kind of unmanifest God that got bored with its loneliness and thus want to 'play'. No such thing at all, the stream of consciousness has always been inseparable from conditions without beginning for countless lifetimes, and there is no ultimate beginning state 'prior manifestation'. Even the nothingness of deep sleep is just another illusory phenomena, another transient state no less empty than any other appearance, like dreams and illusions. So is the pure formless presence realized in I AM yet another manifestation -- no more/less purer, no more/less empty and no more/less luminous than pure sight-presence-consciousness and so on.

But the dependent origination and emptiness is deep and will need some time to discover its depths and profundity.

tl/dr: this moment of consciousness is the total exertion/dependent origination of all conditions of all times and all space, which includes importantly, a previous moment of consciousness (and this stream of consciousness can be traced back into infinite past and will continue into infinite future).

Consciousness is the momentary manifestation/appearance of each moment, and not some kind of background and substratum. A permanent consciousness or substratum is Advaita view, not in line with Buddhist insight of anatta.