The word "linen" has more than one meaning in modern English. In this particular instance, it refers to a fabric that is made from flax. If you can show me a garment that is woven from wool and flax, then I will avoid wearing it.
Let's see... How can we avoid marrying Hittites, Girgashites, Amorites , Canaananites, Perrizzites, Hivites or Jebusites? Most of my friends are married, but none of them have married people from any of those nations. I'm not sure, but I think it might have something to do with the fact that those nations don't exist any more, so it would be much harder to violate that particular commandment than to keep it.
That commandment is repeated a few chapters later, with a little more detail...
You shall make yourself tassels on the four corners of the garment with which you cover yourself. (Deu. 22:12 ESV)
Do you actually have a garment that has four corners on it? Most people don't. I do have such a garment. It's called a tallit and it does indeed have tassels on all four corners with a techelet (blue) thread in each tassel. In fact, that's why I bought it - to be able to obey God's commandment.
Sorry for taking your post a little out of order, but there were three commandments that really were all about the same thing, so I put them together at the end.
All of those commandments concern sacrifices, and the answer for all of them is the same. The only places where valid sacrifices could be offered were the tabernacle and later the temple in Jerusalem. Also, the people didn't offer the sacrifices themselves. They gave the lambs, grain or other offerings to the priest and the priest made the sacrifice. Since there is neither a temple nor tabernacle where the offerings can be made, nor a functioning Aaronic priesthood, it would be a sin for us to offer sacrifices today. An interesting thing concerning sacrifices is that Jesus told people to offer sacrifices. When he healed lepers, he told them to go and show themselves to the priests to be cleansed according to the law. That involved offering a sacrifice. Why did he do that if he came to do away with them?Also, the first Christians continued to offer sacrifices while the temple still stood. Paul had made a vow and offered a sacrifice when he had completed that vow (Acts 18:18) and paid for the sacrifices for others who had made a vow (Acts 21:23-24). That last verse also says that Paul kept the law. He also told Gentiles to keep the feast of Passover and Unleavened Bread, which involved making a Passover sacrifice (I Cor. 5:8).
The TOG