Curl: (60) SSL certificate problem: unable to get local issuer certificate

user@notebook:~$ echo "QUIT" | openssl s_client -connect SERVER.de:443 -CApath /etc/ssl/certs  
CONNECTED(00000003)
depth=0 OU = Domain Control Validated, CN = *.SERVER.de
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 OU = Domain Control Validated, CN = *.SERVER.de
verify error:num=21:unable to verify the first certificate
verify return:1
---
Certificate chain
 0 s:/OU=Domain Control Validated/CN=*.SERVER.de
   i:/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA
---
Server certificate
-----BEGIN CERTIFICATE-----
(...)
-----END CERTIFICATE-----
subject=/OU=Domain Control Validated/CN=*.SERVER.de
issuer=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA
---
No client certificate CA names sent
Peer signing digest: SHA512
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 2418 bytes and written 302 bytes
Verification error: unable to verify the first certificate
---
New, TLSv1.2, Cipher is EC123-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : EC123-RSA-AES128-GCM-SHA256
    Session-ID: 969321
    Session-ID-ctx:
    Master-Key: FB0DA888F2B34568753534FF828CBB96CCC6C246352696F13E3DBD1D1CBB7692389E3B1C2B8DD5F3A3EB759A1D730F6
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    TLS session ticket lifetime hint: 300 (seconds)
    TLS session ticket:
    0000 - 95 f5 93 10 f2 8b 44 6a-d7 7f e5 be be db 96 51   ......Dj.......Q
    0010 - 71 3f 17 dd ad 08 ea c0-53 90 1b 15 0c be 26 49   q.......S.....&I
    0020 - ec 91 39 f3 07 1f 97 a4-97 8d 27 e7 9e fb 9f 81   ..9.......'.....  
    0030 - f6 6a 89 5a 67 82 e4 05-83 3f 25 ef ed 00 46 5d   .j..g....?%...F]
    0040 - df ad 42 2d fb e8 b7 89-c8 0b 22 88 84 40 f9 c7   ..B-......"..@..  
    0050 - e9 60 b0 71 2c 06 bb f7-de e2 39 46 84 73 1b 7f   .`.q,.....9F.s..
    0060 - 63 8f cf 27 8d 2f c1 62-77 3d f6 2d 5e 81 13 5d   c..'./.bw=.-^..]  
    0070 - 0f 30 c0 87 63 a1 a8 cc-c5 6a 55 cd b7 2f a1 db   .0..c....jU../..
    0080 - 37 f3 9d c9 79 cb 2b 46-c9 bf f1 ee 0a 4e d3 cd   7.....+F.....N..
    0090 - 71 4d f8 50 fb e9 de 87-cb 73 98 64 49 b2 ae 15   qM.P.....s.dI...
    00a0 - bb 6d f7 21 e4 69 a1 4a-83 14 c4 70 f7 bc df 5b   .m.!.i.J...p...[

    Start Time: 1574523120
    Timeout   : 7200 (sec)
    Verify return code: 21 (unable to verify the first certificate)
    Extended master secret: no
---
DONE