I’ve written an https server in C++ using cpp-httplib (https://github.com/yhirose/cpp-httplib). My requirement is that it needs to work with pre-shared key and cipher DHE-PSK-AES256-CBC-SHA or DHE-PSK-AES256-CBC-SHA384.
I understand those are TLSv1 ciphers that are considered weak, therefore they are somewhat disabled by default.
Here is the relevant part of my code:

httplib::SSLServer *const ssl_server = new httplib::SSLServer([](SSL_CTX &context)
{
    SSL_CTX_set_psk_server_callback(&context, psk_callback);

    return true;
});

SSL_CTX *const context = ssl_server->ssl_context();

// Section added later, it doesn't work either.
SSL_CTX_set_security_level(context, 0);
SSL_CTX_set_min_proto_version(context, TLS1_VERSION);
SSL_CTX_set_max_proto_version(context, TLS1_VERSION);

SSL_CTX_set_cipher_list(context, "DHE-PSK-AES256-CBC-SHA:DHE-PSK-AES256-CBC-SHA384");
SSL_CTX_set_ciphersuites(context, "");
// End of section added later.

ssl_server->listen("0.0.0.0", 50051);

The section enclosed between comments has been added later, when I noticed the handshaking was picking more modern ciphers (TLS_CHACHA20_POLY1305_SHA256 and such), which won’t work in the final setup.
I understand a way to test the connection would be with openssl s_client command:

openssl s_client -connect localhost:50051 -psk ... -tls1 -cipher 'DHE-PSK-AES256-CBC-SHA:@SECLEVEL=0'

Sadly, I get the following output:

CONNECTED(00000003)
408764833A7B0000:error:0A000410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:../ssl/record/rec_layer_s3.c:1599:SSL alert number 40
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 66 bytes
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1
    Cipher    : 0000
    Session-ID: 
    Session-ID-ctx: 
    Master-Key: 
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1733742579
    Timeout   : 7200 (sec)
    Verify return code: 0 (ok)
    Extended master secret: no
---

If I start a test server with openssl s_server command:

openssl s_server -accept 50051 -nocert -psk ... -tls1 -cipher "DHE-PSK-AES256-CBC-SHA:@SECLEVEL=0"

The openssl s_client command gives me the following output (which I understand is the one I need for my server):

CONNECTED(00000003)
Can't use SSL_get_servername
---
no peer certificate available
---
No client certificate CA names sent
Server Temp Key: DH, 3072 bits
---
SSL handshake has read 1131 bytes and written 541 bytes
Verification: OK
---
New, SSLv3, Cipher is DHE-PSK-AES256-CBC-SHA
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1
    Cipher    : DHE-PSK-AES256-CBC-SHA
    Session-ID: 5651AD5A635DFB1E723C1CEE31769765C42930899431C4E8E55694BAA6193756
    Session-ID-ctx: 
    Master-Key: 6771FA4460BF6B1E5D96F4957F6C3B27AFCCDC2F7E3C2676775E02E9FE0DC9B1E3F5AD576AC3BE203D6362876E8347CB
    PSK identity: Client_identity
    PSK identity hint: None
    SRP username: None
    TLS session ticket lifetime hint: 7200 (seconds)
    TLS session ticket:
    0000 - ab 65 ec 02 38 eb 69 27-6e 1f 14 47 b3 aa 17 49   .e..8.i'n..G...I
    0010 - b3 59 01 fb 54 33 e1 0a-71 14 d4 cc d8 be 50 e4   .Y..T3..q.....P.
    0020 - 35 c1 9d 27 5f 73 60 b1-eb bb 8d 3f 46 50 b8 20   5..'_s`....?FP. 
    0030 - 44 fa da ff e9 1a cb 52-db 05 49 84 44 a4 e0 09   D......R..I.D...
    0040 - 98 18 b0 78 2f c4 2d 89-cf 8a a1 10 5f eb a0 47   ...x/.-....._..G
    0050 - 98 b0 c3 b0 51 ed 59 9b-7f 6c e4 40 45 91 13 b6   ....Q.Y..l.@E...
    0060 - b8 4c 57 dc 3f 62 d4 aa-2d 39 75 43 16 ef f7 67   .LW.?b..-9uC...g
    0070 - 6c e4 b2 1c 6b 70 f0 7d-72 7b 46 2f b0 6b a7 e5   l...kp.}r{F/.k..
    0080 - 92 f7 25 1a 63 fa 0c 88-ed be 84 a5 e8 08 6a 60   ..%.c.........j`
    0090 - 64 61 1b f1 ed cc 1e 5e-02 b3 02 55 cd c3 17 16   da.....^...U....
    00a0 - 67 00 de f4 5e 0d 6f 2b-aa a0 5f fc 1d ce 3b f4   g...^.o+.._...;.
    00b0 - ed 51 20 72 5b 0e 02 b6-1f 51 53 3a 8d 19 af dd   .Q r[....QS:....

    Start Time: 1733744221
    Timeout   : 7200 (sec)
    Verify return code: 0 (ok)
    Extended master secret: yes
---

I’ve been things for almost a week, but I wasn’t able to make it work with the desired cipher. My knowledge of openssl is just not enough for me to understand what I’m doing wrong. Is anybody able to help me, please?