I have several linux boxes with opensuse, manjaro and arch and in each case cut and past now fails to work from firefox to librewriter. Middle mouse button, by far the best way of cut and paste, just randomly fails. Ctl-v, which is not even usable in most unix aps, also fails. My windowmanager is usually wmaker.
Currently using LO v5.4.1.2 (but started with 4.x) have not seen problem you are experiencing in Mint (many versions), Ubuntu, Debian, Xubuntu, and for a short time Manjaro. Ctl-c,v works from a variety of places including Firefox & Chrome.
Ctl-V is not a mean s of cutting and pasting, but it also doesn’t work.
Version: 5.4.1.2.0+
Build ID: 5.4.1-1
CPU threads: 8; OS: Linux 4.6; UI render: default; VCL: gtk3;
Locale: en-US (en_US.UTF-8); Calc: group
cut and paste should be drag and middle click.
There is no cutting from browser. Currently using Mint 18.2 & no problem with select text, middle click, then middle click in writer. This is a middle click from writer:
Version: 5.4.1.2
Build ID: ea7cb86e6eeb2bf3a5af73a8f7777ac570321527
CPU threads: 4; OS: Linux 4.8; UI render: default; VCL: gtk2;
Locale: en-US (en_US.UTF-8); Calc: group
Also highlighting text then drag & drop work.
Sorry, edit on last got screwed up. Had to re-post.
Just as another test, copying to and from writer and terminal also work here with middle click. My version is from LO. If you are using a PPA version possible problem there?