Some further observations:
In spite of the seemingly slow CPU it works surprisingly fluid for my PDF reading needs. The native PDF reader is able to manage some huge PDF files with a size of up to 210MB and with over 1000, 2000 or even 12300 pages! First load of such huge files takes about a dozen seconds, but then page display works mostly without ghosting and completes at a fraction of a second at every page turn.
On the other hand, there is a freely available 102MB PDF file of rather doubtful PDF quality (but excellent reading material) with a thesis about
'The Conga Drum' by Alex Pertout that can be used to reliably crash the PDF reader software after some annoyingly slow page turns...
As already mentioned before, dictionary integration leaves to be desired, as external dictionaries are not used, but only a static built in one with English-Chinese. After inquiry with the vendor/manufacturer and explaining why this is a very important feature, they promised to fix this soon ("i hope end of this month can have new update firmware by OTA"). Time will tell if the manufacturer is able to provide timely software enhancements and firmware updates.
Being a Linux user since over 20 years i used to be very happy with the inherent simplicity of mounting external storage of other e-ink readers as normal block devices via USB. I manage my book library within a hierarchy of folders using the 'Midnight Commander' file manager instead of something like Calibre, because this is the most simple and straightforward approach for me.
Unfortunately, this is not as simple anymore with the Likebook Note where i have to resort to access the device via MTP. I have mixed results trying this in Debian Linux with kernel 4.17.8 using the jmtpfs utility. Sometimes it works and sometimes it doesn't, and if it works it doesn't appear to be very reliable and transfer speed is rather slow. These are the moments making me despair about the rather backwards results of so called technical progress...