Hi,
first of all, thank you for this awesome editor, great work.

On Linux (CentOs 7.5) I'm having a crash when I try to open a directory after pressing ctrl+o.

After some investigation I probably found the issue.
On CentOs the default file system type is Xfs and according to this guy the d_type of a readdir always returns 0 on Xfs. It looks like that behaviour still is accurate and 4ed cannot figure out if something is a directory, link or file.

Thanks for the report and extra info. I'm not sure what I can do about this yet, but I'll take a look. Ultimately I might have to set up an emulator to fix this so it could be a little while before it's fixed.