Note to Linux users that use Debian-derivatives (like Ubuntu, Linux Mint) and the
Foliate PPA: The label has changed from "Foliate ebook reader" to "Foliate" in between versions 2.6.3 and 2.6.4.
This means that—for safety reasons—GUI-based updaters (like in Linux Mint) will show a message, but
stop updating until you have manually accepted that change (and thus "allowed" it).
The easiest way to do that on Debian-like systems is performing a
sudo apt update in the terminal,
confirm the change, and then do a
sudo apt upgrade afterwards to actually get the newer version.