Without there being any certain solid objective reality out there in space, still we grasp at perceptions of the world as if they are real. Perceived objects do not exist inherently, but we do perceive them as if they exist objectively. This is Relative Truth. External appearances do exist in terms of Relative Truth, but this is not the real truth. It is ignorance.
But what about other sentient beings? Our perceptions of them are ultimately illusions. Are they empty phenomena and lacking any inherent existence? Yet all of them also possess the Natural State and are as equally caught up in their unreal projections as we are, depending on their individual and collective karmic causes. What can we do to help to liberate them from their suffering in Samsara?
Ah, now if you are interested in what is being pointed at above, I’d suggest looking up the term “Twofold Emptiness” … but really, there is no “self”, you just are seemingly mistaken about the Nature of Reality  eh ? 🙏
Please note : I mean no offence, however when it comes to Immediate Direct Experience where can we look except to our own Minds !
 Oh, perhaps along “similar lines” is Francis Tiso’s book the Rainbow Body and Resurrection eh ?
Tiso describes the spiritual practices that give rise to the rainbow body and traces their history deep into the encounter of religions in medieval Central Asia. His erudite exploration of the Tibetan phenomenon raises the fascinating question of whether there is a connection between the rainbow body and the dying and rising of Jesus.
And, although I haven’t got round to reading it all yet, there is Jean-Luc Achard’s book Enlightened Rainbows eh ?
Shardza Rinpoche is one of the most famous Bon po masters of the late 19th century and early 20th century. He is of course particularly well-known because of his realization of the Rainbow Body (‘ja’ lus) which he manifested at the end of his life in 1934