As I am getting a 404 today on the download link on Mobileread for sergkv12's updated version I am attaching a copy of version 3.1.2-52 built on 2020-03-14. Pocketbook firmware 5 version.
Looking at the Russian site the current link is
https://cloud.mail.ru/public/2ro8/5hrvCbiNg.
Best
IDS