@ViaCrucis
I'll give some links:
Link 1
Link 2
You can research the archeology findings of the hieroglyph Renpet, the tomb of Qubbet el-Hawa, Deir El-Medina (Village). There's a lot more, but like I said to JSRG, I just don't have the time to go over it. My cats surgery was unexpected. I'll give you more info when I get more time.
Note: Due to some kind of bug on the forums, if I quote this post and it includes the links within "Link 1" and "Link 2", it encounters an error and refuses to post this reply. So I had to edit the quote to remove the links themselves (so it only says "Link 1" and "Link 2" as simple text), but someone can go back to the original post to look at them. But anyway, let's talk about them.
Link 1 does not appear to be a scholarly source in any way, and claims "At the winter solstice, in anticipation of Ra’s return, the Egyptians would fill their homes with green date palm rushes that symbolized Ra’s recovery and triumph over death." As its source, it links to an article on The History Channel's website (the channel that airs "Ancient Aliens") which claims without citation that "At the winter solstice, when Ra began to recover from his illness, the Egyptians filled their homes with green palms and papyrus reeds to symbolize the triumph of life over death." So we have a non-scholarly source citing a non-scholarly source which itself gives no citation. This means it provides no evidence for the claim.
Link 2 does look to actually be scholarly (its author appears to be a professor of Graeco-Roman archaeology), and it includes plenty of footnotes. So this looks to be a much more valid source than the first. This article discusses the use of palm trees (and especially palm branches), primarily in Egypt but with a look towards some neighboring cultures like the Greeks or Israel. However, we run into a problem: Your claim was that "Putting a tree in your house is linked to the winter solstice to celebrate the god Ra." But unless I am missing something, in this article there is no mention of Ra, no mention of the winter solstice, and no mention of anyone putting up palm trees in their homes. This thus actually casts further doubt on your claim, for if it were true that there was a custom of bringing in palm trees for the winter solstice in celebration of Ra, one would have expected to see it mentioned in this.
Even if this claim about Ra and the solstice was true, however, we run into the other big problem, which both I and ViaCrucis have pointed out. Christmas trees started out in Germany around the year 1500 AD. So even if this claim about Ra was true--and again, that's a big if considering the lack of evidence offered so far--why (and for that matter,
how) would the Germans from around 1500 AD be taking celebration ideas from Egyptian practices that had died out more than a thousand years ago and the Germans would presumably not even be aware of?