@richard67, if the selected file cannot be uploaded because it is larger than the maximum upload size, we have to use the FTP upload method, but I cannot make it work.
Depending on the outcome of the debate raised by @brianteeman , this will require some work.
#27945 (comment)

@wilsonge It seems we need a decision about FTP, if to keep it or if to drop it.

We're keeping it.

I can't make it work with Joomla! 3.x too.
Upload and update Joomla! via FTP does not seem to work.
We have ftp options, but it is not functional.
Has anyone experienced this?

As I understand it, we only use FTP to update (write) files on the server but not to upload the selected file.
In this case, this PR is ready to be tested. It should work like Joomla! 3.x.
Question: Do I have to create a new PR to implement the upload via FTP ?

As I understand it, we only use FTP to update (write) files on the server but not to upload the selected file.

Not as far as my understanding went (admittedly I've never tested FTP Modes). We use JFile::write https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_joomlaupdate/models/default.php#L443 (downloads) and JFile::upload when uploading a zip https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_joomlaupdate/models/default.php#L995

anything using JFile should respect the global configuration settings for FTP - that's the entire point of the JFile class to have the FTP wrapper

Tested locally with XAMPP on Windows 10.

PHP Warning: fileowner(): stat failed for /tmp/330759cc93812163319df93121148c7f in \libraries\src\Filesystem\Path.php on line 279

Tested locally with XAMPP on Windows 10.

PHP Warning: fileowner(): stat failed for /tmp/330759cc93812163319df93121148c7f in \libraries\src\Filesystem\Path.php on line 279

@Quy , which FTP server are you using in Windows 10 (XAMPP is just a web server) ? For example, with the Filezilla server, you must grant privileges to your FTP user.
Have you also correctly defined the root path of your joomla site in the global FTP configuration ?

I have tested this item ? unsuccessfully on 0447602

So I could reproduce the issue but it does not occur every time you select the "write files directly" option. This does not happen when you switch to another option and then switch back to the write files directly option. If you for the first time en ther the tab and switch to that option for the first time when ur in the upload & update tab then this behavior occurs.

After I applied the patch and executed the command npm install this issues was not fixed and the same happened as like I didnt apply the patch.

Tested the patch by following the instructions. Selecting "Write files directly" causes the form fields always to disappear. Selecting second or third option will display the form fields. Is this the expected behaviour?

Previously, the form fields did disappear once. But after selecting around, the form fields were always displayed.

Since the FTP credentials were implemented as a workaround for the wwwrun problem on web servers, such a server is necessary for a reliable test.

Windows with xampp is the wrong system for this.

A Unix based system with Apache and PHP as mod_php/apache2handler is required to test the correct use of FTP credentials.

Do we have testers with such a base here?