TLS issue with serve ftp

What is the problem you are having with rclone?

I'm trying to serve a webdav remote via ftp using tls, but on FileZilla it works, but in my Plesk installation doesn't connect because it tests with the following command:
curl -v -P - --ssl -k -u my_user 'ftp://127.0.0.1:2121/my_folder/'

failing.

What is your rclone version (output from rclone version)

rclone v1.55.0-beta.5274.ff6868900
- os/arch: linux/arm
- go version: go1.16

Which OS you are using and how many bits (e.g. Windows 7, 64 bit)

Raspbian GNU/Linux 10 (buster)

Which cloud storage system are you using? (e.g. Google Drive)

WebDav

The command you were trying to run (e.g. rclone copy /tmp remote:tmp)

rclone serve ftp RemoteWebDav:/Backup/ --addr 0.0.0.0:2121 --user my_user --pass my_password --vfs-cache-mode writes --vfs-cache-max-size 1G --cert /home/pi/sslp/cert.pem --key /home/pi/sslp/key.pem --config /home/pi/.config/rclone/rclone.conf

A log from the command with the -vv flag (e.g. output from rclone -vv copy /tmp remote:tmp)

2021/03/15 19:02:04 DEBUG : Using config file from "/home/pi/.config/rclone/rclone.conf"
2021/03/15 19:02:04 DEBUG : rclone: Version "v1.55.0-beta.5274.ff6868900" starting with parameters ["rclone" "serve" "ftp" "IceDrive:/Backup/srv3_dnswave_eu" "--addr" "0.0.0.0:2121" "--user" "my_user" "--pass" "my_password" "--vfs-cache-mode" "writes" "--vfs-cache-max-size" "1G" "--cert" "/home/pi/sslp/cert.pem" "--key" "/home/pi/sslp/key.pem" "--config" "/home/pi/.config/rclone/rclone.conf" "-vv"]
2021/03/15 19:02:04 DEBUG : Creating backend with remote "RemoteWebDav:/my_folder"
2021/03/15 19:02:04 DEBUG : fs cache: renaming cache item "RemoteWebDav:/my_folder" to be canonical "RemoteWebDav:/my_folder"
2021/03/15 19:02:04 INFO  : webdav root 'my_folder': poll-interval is not supported by this remote
2021/03/15 19:02:04 DEBUG : vfs cache: root is "/root/.cache/rclone/vfs/RemoteWebDav/my_folder"
2021/03/15 19:02:04 DEBUG : vfs cache: metadata root is "/root/.cache/rclone/vfs/RemoteWebDav/my_folder"
2021/03/15 19:02:04 DEBUG : Creating backend with remote "/root/.cache/rclone/vfs/RemoteWebDav/my_folder"
2021/03/15 19:02:04 NOTICE: webdav root 'my_folder': Serving FTP on 0.0.0.0:2121
2021/03/15 19:02:04 INFO  : vfs cache: cleaned: objects 0 (was 0) in use 0, to upload 0, uploading 0, total size 0 (was 0)
2021/03/15 19:02:04 INFO  : : Rclone FTP Server listening on 2121
2021/03/15 19:02:23 DEBUG : : NewDriver: Init driver
2021/03/15 19:02:23 DEBUG : : >NewDriver:
2021/03/15 19:02:23 INFO  : 2a1037dffef2eb2e426f: Connection Established
2021/03/15 19:02:23 INFO  : 2a1037dffef2eb2e426f: < 220 Welcome to Rclone v1.55.0-beta.5274.ff6868900 FTP Server
2021/03/15 19:03:04 INFO  : vfs cache: cleaned: objects 0 (was 0) in use 0, to upload 0, uploading 0, total size 0 (was 0)
2021/03/15 19:04:04 INFO  : vfs cache: cleaned: objects 0 (was 0) in use 0, to upload 0, uploading 0, total size 0 (was 0)
2021/03/15 19:04:24 INFO  : 2a1037dffef2eb2e426f: Connection Terminated

Start with the rclone serve ftp entry point and reproduce the TLS connection using the provided curl command against the supplied command line. Compare that behavior with the successful FileZilla connection; done means the Plesk curl command can establish the expected authenticated FTP/TLS session.