Copy-paste from a web page to a text file

Hello everyone, I hope you are doing well. I'm writing this message to find a solution. To explain: right now I'm copying and pasting content from a blog I've created into a text file (I'm using Libre Office) (to have a copy): it's great because it retains the original bold and italic characters, but not the strikethrough or underlined ones. I'd like to know why the copy-paste does not work with strikethrough and underlined characters? And how, apart from manually (which I'm doing, but it's time-consuming), could I directly copy and paste the strikethrough and underlined characters as well?

I'm not sure if I'm being very clear, but anyway. I hope someone can help me. Thanks in advance.