Having installed the update on my device and read through some threads (
https://papierlos-lesen.de/tolino-fi...chienen-70139/ being another German source), this seems to be the summary:
Fonts added:
Atkinson Hyperlegible
Noto Sans
Texturina
Ubuntu
Fonts removed:
Fira Sans
Source Sans
Droid Serif
Hidden menu that let you select the reading engine appears to have been removed
Some supposed stability improvements
Access to the Skoobe subscription book service added - unclear on which devices and which brandings, confirmed so far for thalia devices from the Vision 3 onwards.