For me, this FTPS issue is quite new. It illustrates how long I have not used it, even though it has been set up in each of my LibreELEC installations for years. A downgrade to LibreELEC 11.0.6 is not an option for me, nor are the latest nightlies of v13, as in this case, FTPS incorrectly lists elements (folders/files).
Through a valuable tip from another post by vpeter on how to overlay files in the file system, I have found a provisional solution. I extracted the files curl and libcurl.so.4.8.0 from the LibreELEC 11.0.6 images (Gen eric.x86_64|RPi2.arm). The two required files are hidden within the archive in the SYSTEM file, located in the directory structures /usr/bin/curl and /usr/lib/libcurl.so.4.8.0. For Windows users, extracting works well with the PeaZip free archiver utility, as the SYSTEM file is also gz compressed.
Once the two files are available, it is time to copy them to your current LibreELEC installation. For this purpose, SSH must be enabled on LibreELEC.
Default access for ssh/sftp:
ssh root@<LibreELEC-IP>
user: root
pass: libreelec
Via SFTP, the two required files are copied to the /storage/ directory. For Windows users, the tool WinSCP is recommended, but the display of hidden files must be enabled beforehand; otherwise, you will not be able to see the hidden .config directory. The file autostart.sh in /storage/.config/autostart.sh is added with the two commands listed below. Ensure that the file attributes for both files for fully functionallty are set back to rwxr-xr-x. Then reboot the media center, and FTPS should function again.
autostart.sh
#!/bin/sh -e
# curl and libcurl.so.4.8.0 extracted from LibreELEC 11.0.6
mount -o bind /storage/libcurl.so.4.8.0 /usr/lib/libcurl.so.4.8.0
mount -o bind /storage/curl /usr/bin/curl
exit 0
This is approximately what the contents of the /storage/ directory look like:

For those who do not want to experience any headaches or wish to avoid the entire process of extraction, I am offering these two files. This is of course a matter of trust. libcurl.so.4.8.0 and curl.zip