You have to mark the target range before you paste the formula. To mark a range without mouse enter the range address into the “Name Box” field top-left of the grid and hit Enter. Or you can name the target range via Sheet > Named Ranges and Expressions. Then you can select this range from the drop-down-list of the “Name Box” field.
Method A: Write F1:F100000 into the name field, Enter. Click in input line and write =E1*2. Press Alt+Enter.
Method B: Write =E1*2 into cell F1, Enter. Write F1:F100000 into name field, Enter. Press Ctrl+D for to fill down.
Method C: Write =E1*2 into cell F1, Enter. Set cell cursor to F1, Ctrl+C. Enter F2:F100000 into name field, Enter. Ctrl+V.
Please do exactly as I describe it, especially where to write something and when to press Enter. Try the methods with an separate spreadsheet and the simple formula =E1*2. In case your real formula is complex, it might take a while to fill and recalculate 100000 cells. Which version of LibreOffice do you use, which operating system?