No one who knows their Bible will ever suggest that God is NOT a Spirit. And the Holy Spirit is Spirit by definition. But Jesus in Heaven is not simply Spirit. Stephen literally saw the heavens opened and Jesus standing at the right hand of God. But to go from their and spiritualize everything is certainly not what Christ taught.
That was Gnostic nonsense.
Even Heaven --
which is the ultimate spiritual realm -- is real, visible, tangible, solid, and yet a totally different realm from the earth and earthy things. Heavenly gold and precious stones may resemble those which are earthly, yet they are truly heavenly. That is why heavenly gold -- for example -- is transparent
"and the city was pure gold, like unto clear glass" (Rev 21:18). Only when we get to Heaven will we see what this consists of, and why there are streets of gold in Heaven, possibly for this reason --
"The gold that John saw in heaven was of such quality that it appears to be transparent in order to reflect the pure light of God’s blazing glory."
Will there literally be streets of gold in heaven?