I have just downloaded Libre Office 5.2. Libre Writer still has the longstanding bug of not being able to search and replace a manual page break. It will find the page break in a search, but when you try to replace it the original page break remains.
Unfortunately, I cannot use Libre Writer because of this bug, and I’m still stuck with Microsoft Word. If you’d fix it, I’d even make a donation to the project!
(I understand there is an extension that supposedly does this, but it behaves in the same manner.)