The latest version can be found here:

https://stupidbeauty.com/?_=/article/1908/HxFtpServer:%20Hx%20FTP%20Server,%20a%20simple%20FTP%20server%20application%20for%20Android

Precompiled old version:

https://stupidbeauty.com/ArticleImages/1907/HxFtpServer.4623.2023.4.4.e.apk

This application will start a FTP server, which enables you to operate the files in the external storage of your phone with a computer FTP client.

Launch this application, and connect to the FTP url shown on the screen with your computer FTP client.

This application need to read and write the external storage for its basic functionality to work correctly.