My problem with nautilus is that it sometimes freezes when copying/deleting files, making me forced to force stop it. So, I have decided to use dolphin instead. How do I make it the default now? (There is no GUI way to do this afaik)
xdg-mime default org.kde.dolphin.desktop inode/directory
There is a good chance the problem is at the system level and won’t be solved by changing the file manager. You need to look for details using the journal as documented in https://docs.fedoraproject.org/en-US/quick-docs/viewing-logs/. The system journal collects massive details, so it can take some effort to find entries related to your issue. It can be useful to post the output from running inxi -Fzxx in a terminal as pre-formatted, web searchable text. This will allow to understand your system configuration, and also makes it possible for others with similar issues and system configurations to find this topic.
I edited a typo in your inxi command. It was inxj before the change.
Thanks!