Same as in title - How can I keep line breaks from diffrent note app when copy -> paste in notion?
It really depends how you are looking to have those line breaks. For example you can have 2 paragraphs and when pasting them, end with 2 text blocks and no space (empty block) between them.
You can have the same with an empty block between them as a space.
Other one is to have everything in the same block, including the line breaks.
I believe you are looking for everything and you can try a code block, paste there and then just change it to text. You will end up with the complete text in one block, including the line breaks.
If you want them with an empty block between them, you will have to paste and hit the + at the right to add a line break below the paragraph.
Hope that helps.