Your comments
Couldn't look at it before today (tough week).
Your epub file archive (epub are zip files) is corrupted. I could not open it with my usual epub app.
The fix is simple though: uncompress the content of the epub file with a compression tools that tolerates erros (7zip worked for me) and compress it again in a new zip file. Then change the extension to ".epub".
If you can send me the file (tom at vaemendis dot net), I'll try to take a look.
The main reason to put a limit at 300 was that this setting is changed through a slider in the admin screen.
If the slider allows very big values, most people (who display only a few dozen cover per page) will strugle, as a small move on the slider will increase the value very quickly.
Until a better option is available, you can try to manually edit the configuration file to set the desired value (do it while Ubooquity is stopped, otherwise it will be overwritten).
Comics are sorted alphabetically, this means 1 comes before 10, 11, etc.
Add zeros in front of the numbers so that they all have the same number of digits (01, 01, 03...10, 11...) and the problem is solved.
With a bit of work, yes.
See this topic:
Next version will be compatible with Java 11+ (this part of the dev is already done).
Max theoritical size for the database file is 4 GB on FAT32 file systems and 4 TB on more modern ones: http://www.h2database.com/html/advanced.html#limits_limitations
But the issue might also lie with the database queries Ubooquity uses, they might be too heavy for really big databases, hard to say.
The logs show a number of dotNet errors
Ubooquity being written in Java, that is weird. ;)
Post the logs anyway, they might tell us a bit more about the issue.
The "+10" is indeed by design.
If you want to go to a specific page, click on the page number (middle of the top bar) and select its number on the pop-up menu.
To see the last page you can also just revert the display order in the options.
Customer support service by UserEcho
Instructions are here:
https://vaemendis.github.io/ubooquity-doc/pages/faq.html#how-can-i-change-the-admin-password-once-it-has-been-set-