Thanks for your comment @Anonymous.
It's good to know my debug work has been useful... ;)

Hello,

I was faced with this segfault when downloading a file from FileZilla server 1.3.0 :

~ # wget -c ftps://192.168.137.243/test.zip -O /var/tmp/test.zip
--2022-03-03 11:39:46--  ftps://192.168.137.243/test.zip
           => '/var/tmp/test.zip'
Connecting to 192.168.137.243:21... connected.
==> AUTH TLS ... WARNING: cannot verify 192.168.137.243's certificate, issued by 'CN=filezilla-server self signed certificate':
  Self-signed certificate encountered.
    WARNING: certificate common name 'filezilla-server self signed certificate' doesn't match requested host name '192.168.137.243'.
 done.
Logging in as anonymous ... Logged in!
==> PBSZ 0 ... done.  ==> PROT P ... done.
==> SYST ... done.    ==> PWD ... done.
==> TYPE I ... done.  ==> CWD not needed.
==> SIZE test.zip ... 3269601
==> PASV ... done.    ==> RETR test.zip ... done.
Length: 3269601 (3.1M) (unauthoritative)
Segmentation fault

My wget was compiled with openssl 1.1.1i library.
And the segfault occured when resuming the SSL session for the data transfer. At this time, the session previously saved in ctx->sess is no more valid (it has been changed by the openssl lib). This is apparently a specific behavior in openssl when using TLS 1.3.

Here you are my patch for this issue in wget 1.21.3:

--- org/src/openssl.c 2022-03-03 11:19:09.513659802 +0100
+++ new/src/openssl.c 2022-03-03 11:29:48.870596212 +0100
@@ -825,6 +825,7 @@
     {
       /* attempt to resume a previous SSL session */
       ctx = (struct openssl_transport_context *) fd_transport_context (*continue_session);
+      ctx->sess = SSL_get0_session (ctx->conn);
       if (!ctx || !ctx->sess || !SSL_set_session (conn, ctx->sess))
         goto error;
     }