Hi!
Sorry for not being able to post DietPi’s system info, but I cannot login to DietPi anymore and hence not retrieve the info any longer.
I use WinSCP latest version and one day all of a sudden it stopped working when trying to log in. My DietPI system is a RPi 3 aamd64 v7 runnning Bullseye v11 as far as I know.
I use latest stable DietPi (v8.16 I assume). And the whole system works normally, sends emails, installed packages run fine (e.g. Pihole, Bitwarden, etc.) - I just cannot WinSCP into it. 
Here is WinSCP’s log of the login process:
. 2023-05-04 19:12:44.348 --------------------------------------------------------------------------
. 2023-05-04 19:12:44.348 WinSCP Version 5.21.8 (Build 13000 2023-04-11) (OS 10.0.19044 - Windows 10 Enterprise)
. 2023-05-04 19:12:44.348 Configuration: HKCU\Software\Martin Prikryl\WinSCP 2\
. 2023-05-04 19:12:44.348 Log level: Debug 1, Logging passwords
. 2023-05-04 19:12:44.349 Local account: XXX
. 2023-05-04 19:12:44.349 Working directory: C:\Program Files (x86)\WinSCP
. 2023-05-04 19:12:44.349 Process ID: 8492
. 2023-05-04 19:12:44.361 Ancestor processes: explorer, ...
. 2023-05-04 19:12:44.361 Command-line: "C:\Program Files (x86)\WinSCP\WinSCP.exe"
. 2023-05-04 19:12:44.362 Time zone: Current: GMT+2, Standard: GMT+1 (Mitteleuropäische Zeit), DST: GMT+2 (Mitteleuropäische Sommerzeit), DST Start: 26.03.2023, DST End: 29.10.2023
. 2023-05-04 19:12:44.362 Login time: Donnerstag, 4. Mai 2023 19:12:44
. 2023-05-04 19:12:44.363 --------------------------------------------------------------------------
. 2023-05-04 19:12:44.363 Session name: raspberry Pi 3 (Bullseye v11) (Site)
. 2023-05-04 19:12:44.363 Host name: 192.168.66.53 (Port: 22)
. 2023-05-04 19:12:44.363 User name: root (Password: XXX, Key file: No, Passphrase: No)
. 2023-05-04 19:12:44.363 Tunnel: No
. 2023-05-04 19:12:44.363 Transfer Protocol: SFTP
. 2023-05-04 19:12:44.363 Ping type: Off, Ping interval: 30 sec; Timeout: 15 sec
. 2023-05-04 19:12:44.363 Disable Nagle: No
. 2023-05-04 19:12:44.363 Proxy: None
. 2023-05-04 19:12:44.363 Send buffer: 262144
. 2023-05-04 19:12:44.363 Compression: Yes
. 2023-05-04 19:12:44.363 Bypass authentication: No
. 2023-05-04 19:12:44.363 Try agent: Yes; Agent forwarding: No; KI: Yes; GSSAPI: Yes
. 2023-05-04 19:12:44.363 GSSAPI: KEX: No; Forwarding: No; Libs: gssapi32,sspi,custom; Custom:
. 2023-05-04 19:12:44.363 Ciphers: aes,chacha20,blowfish,3des,WARN,arcfour,des; Ssh2DES: No
. 2023-05-04 19:12:44.363 KEX: ecdh,dh-gex-sha1,dh-group14-sha1,rsa,WARN,dh-group1-sha1
. 2023-05-04 19:12:44.363 SSH Bugs: Auto,Auto,Auto,Auto,Auto,Auto,Auto,Auto,Auto,Auto
. 2023-05-04 19:12:44.363 Simple channel: Yes
. 2023-05-04 19:12:44.363 Return code variable: Autodetect; Lookup user groups: Auto
. 2023-05-04 19:12:44.363 Shell: default
. 2023-05-04 19:12:44.363 EOL: LF, UTF: Auto
. 2023-05-04 19:12:44.363 Clear aliases: Yes, Unset nat.vars: Yes, Resolve symlinks: Yes; Follow directory symlinks: No
. 2023-05-04 19:12:44.363 LS: ls -la, Ign LS warn: Yes, Scp1 Comp: No; Exit code 1 is error: No
. 2023-05-04 19:12:44.363 SFTP Bugs: Auto,Auto
. 2023-05-04 19:12:44.363 SFTP Server: default
. 2023-05-04 19:12:44.363 Local directory: XXX, Remote directory: /usr/bin, Update: Yes, Cache: Yes
. 2023-05-04 19:12:44.364 Cache directory changes: Yes, Permanent: Yes
. 2023-05-04 19:12:44.364 Recycle bin: Delete to: No, Overwritten to: No, Bin path:
. 2023-05-04 19:12:44.364 DST mode: Unix
. 2023-05-04 19:12:44.364 --------------------------------------------------------------------------
. 2023-05-04 19:12:44.418 Looking up host "192.168.66.53" for SSH connection
. 2023-05-04 19:12:44.419 Connecting to 192.168.66.53 port 22
. 2023-05-04 19:12:44.423 Connected to 192.168.66.53
. 2023-05-04 19:12:44.464 Waiting for the server to continue with the initialization
. 2023-05-04 19:12:44.464 We claim version: SSH-2.0-WinSCP_release_5.21.8
. 2023-05-04 19:12:44.464 Detected network event
. 2023-05-04 19:12:44.464 Connected to 192.168.66.53
. 2023-05-04 19:12:44.512 Detected network event
. 2023-05-04 19:12:44.512 Waiting for the server to continue with the initialization
. 2023-05-04 19:12:44.512 Remote version: SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
. 2023-05-04 19:12:44.512 Using SSH protocol version 2
. 2023-05-04 19:12:44.517 Have a known host key of type ssh-ed25519
. 2023-05-04 19:12:44.517 Have a known host key of type ecdsa-sha2-nistp256
. 2023-05-04 19:12:44.517 Have a known host key of type ecdsa-sha2-nistp521
. 2023-05-04 19:12:44.520 Detected network event
. 2023-05-04 19:12:44.520 Waiting for the server to continue with the initialization
. 2023-05-04 19:12:44.522 Doing ECDH key exchange with curve Curve25519 and hash SHA-256
. 2023-05-04 19:12:44.587 Detected network event
. 2023-05-04 19:12:44.587 Waiting for the server to continue with the initialization
. 2023-05-04 19:12:44.676 Server also has rsa-sha2-512/rsa-sha2-256/ssh-rsa host keys, but we don't know any of them
. 2023-05-04 19:12:44.677 Host key fingerprint is:
. 2023-05-04 19:12:44.677 ssh-ed25519 255 SHA256:XXX
. 2023-05-04 19:12:44.677 Verifying host key ssh-ed25519 0x3bbXXX 7b3bdXXX b23fXXX ccbfXXX ,0x5XXX ab00XXX dc0bXXX 6121XXX with fingerprints ssh-ed25519 255 SHA256:XXX ssh-ed25519 255 11:ce:16:XXX
. 2023-05-04 19:12:44.728 Host key matches cached key
. 2023-05-04 19:12:44.728 Initialised AES-256 SDCTR (AES-NI accelerated) [aes256-ctr] outbound encryption
. 2023-05-04 19:12:44.728 Initialised HMAC-SHA-256 outbound MAC algorithm
. 2023-05-04 19:12:44.728 Will enable zlib (RFC1950) compression after user authentication
. 2023-05-04 19:12:44.728 Initialised AES-256 SDCTR (AES-NI accelerated) [aes256-ctr] inbound encryption
. 2023-05-04 19:12:44.728 Initialised HMAC-SHA-256 inbound MAC algorithm
. 2023-05-04 19:12:44.728 Will enable zlib (RFC1950) decompression after user authentication
. 2023-05-04 19:12:44.731 Detected network event
. 2023-05-04 19:12:44.731 Waiting for the server to continue with the initialization
. 2023-05-04 19:12:44.736 Pageant is running. Requesting keys.
Here is a screenshot of WinSCP… it just waits for ever for “authentification”:
Regards