Qubes on a solid state usb is my go-to, but this brings the functionality of trustedpdf from qubes to anything that can run a docker container. It appeals to a much wider audience, as disposable Linux boot drives have a significant barrier of entry to the not-so-technical folk.

My only concern here is vm escape and Libre office are two VERY big targets for nation state actors. (libreoffice had an exploit exposed in the vault7 leaks) It's a tradeoff for being able to safely open "totallynotphishingexe.pdf" on windows or osx.