Different user here. I just did a fresh install after not having used LibreOffice in some years.
I’m having the same issue with the display, except that the UI appears to be cut off on all four sides. Not only is it cut off, but it is impossible to actuate the font-list, or font-size drop-downs. The interface only ‘sees’ the cut-off icons. I tried ‘repairing’ because–why not. I also tried uninstalling/reinstalling, and restarting. Neither of these actions resolved the issue.
If by ‘Windows border at the top,’ you mean the narrow, horizontal title bar with the icon in the upper-left which, if clicked shows ‘Restore, […lalala], Maximize, Minimize, Close’–the answer is "yes.’ That appears to be fine, so the problem may lie with the application frame? I only checked the word processor and the spreadsheet applications, and both have the same issue.
My laptop is a Dell XPS. Its display is more or less a ‘letterbox’ aspect ratio. I’m running Windows 10 Education, and the OS is up to date.
Thanks for any info -