A de Sitter universe is fairly similar to the early inflationary epoch of our own universe. It doesn’t consist of “the ether” or anything, it’s just expanding space-time.
That would still follow Lemaitre’s Bible model which is based on expanding (stretching). It’s just amazing how every mention of the Creation of the Heavens in the Bible follows the Big Bang (Expansion Model) and how a Catholic Priest found it to be correct by the redshift of far away galaxies moving away from each other:
Job 09:08 Who alone stretches out the heavens
Isaiah 40:22 [It is] he that sitteth upon the sphere of the earth, and the inhabitants thereof [are] as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in. Note: This is the very first written text on the planet earth that describes the earth as a sphere, or ball. This must have been inspired by God, as ancients could never have imagined anything like that.
42:05 Thus saith God the LORD, he that created the heavens, and stretched them out; he that spread forth the earth, and that which cometh out of it; he that giveth breath unto the people upon it, and spirit to them that walk therein.
44:24 Thus saith the LORD, thy redeemer, and he that formed thee from the womb, I [am] the LORD that maketh all [things]; that stretcheth forth the heavens alone; that spreadeth abroad the earth by myself.
45:12 I stretched out the heavens with My hands.
48:13 Mine hand also hath laid the foundation of the earth, and my right hand hath spanned the heavens: [when] I call unto them, they stand up together.
51:13 And forgettest the LORD thy maker, that hath stretched forth the heavens, and laid the foundations of the earth; and hast feared continually every day because of the fury of the oppressor, as if he were ready to destroy? and where [is] the fury of the oppressor?
Jeremiah 10:12 And by His understanding He has stretched out the heavens.
51:15 He hath made the earth by his power, he hath established the world by his wisdom, and hath stretched out the heaven by his understanding.
Job 09:08 Which alone spreadeth out the heavens, and treadeth upon the waves of the sea. He stretcheth out the north over the empty place, [and] hangeth the earth upon nothing. Note: The first written text on the planet earth that describes the earth as free floating in space. This must have been inspired by God, as ancients could never have imagined anything like that.
37:18 Hast thou with him spread out the sky, [which is] strong, [and] as a molten looking glass?
Psalms 104:02 Who coverest [thyself] with light as [with] a garment: who stretchest out the heavens like a curtain.
Zechariah 12:01 The burden of the word of the LORD for Israel, saith the LORD, which stretcheth forth the heavens, and layeth the foundation of the earth, and formeth the spirit of man within him.