I had a problem with SEF URL.
I have enabled Search Engine Friendly URLs and Use URL Rewriting in Joomla, and of course I also changed htaccess.txt into .htaccess.
But link from jdownloads looks like:
I have enabled Search Engine Friendly URLs and Use URL Rewriting and also changed htaccess.text into .htaccess:
downloads?view=category&catid=2
instead of:
downloads/category/2-uncategorised
The problem was in file legacyrouter.php
Just rename this file to: LegacyRouter.php in: "joomlaroute"/components/com_jdownloads/src/Helper/
My installed versions are: Joomla 5.3.4 and jDownloads 4.0.47
Thanks to user "mhehm" from this topis: https://www.jdownloads.com/forum/index.php?topic=14387.0