Server: cups 1.3.7
Client: Kbuntu 17.04 / Fedora 27 (since cups-Version 2.2.4-2.3b1)

Work: Printing from firefox
Don't Work: Printing from LibreOffice, Okular or lp

~> lp -d lama /etc/hosts
lp: Bad Request

debug2-LogLevel

d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: Write on fd 10...
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: polling 7 fds for 1 seconds...
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: epoll() returned 1...
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: Write on fd 10...
d [02/Jan/2018:13:46:14 +0100] cupsdWriteClient: 10 bytes < 0
d [02/Jan/2018:13:46:14 +0100] cupsdAddSelect: fd=10, read_cb=0x40f013, write_cb=(nil), data=0x59de20
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: polling 7 fds for 1 seconds...
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: epoll() returned 1...
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: Read on fd 10...
d [02/Jan/2018:13:46:14 +0100] cupsdReadClient: 10, used=0, file=-1 state=0
D [02/Jan/2018:13:46:14 +0100] cupsdReadClient: 10 POST /printers/lama HTTP/1.1
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: uri = "/printers/lama"...
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location CUPS_INTERNAL_BROWSE_ACL Limit 0
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /printers/name Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /printers Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /jobs Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /classes/name Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /classes Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /admin/log Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /admin/conf Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location /admin Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: Location / Limit 7f
d [02/Jan/2018:13:46:14 +0100] cupsdFindBest: best = /printers
d [02/Jan/2018:13:46:14 +0100] cupsdAuthorize: con->uri="/printers/lama", con->best=0x555100(/printers)
d [02/Jan/2018:13:46:14 +0100] cupsdAuthorize: Authorization=""
D [02/Jan/2018:13:46:14 +0100] cupsdAuthorize: No authentication data provided.
d [02/Jan/2018:13:46:14 +0100] cupsdIsAuthorized: con->uri="/printers/lama", con->best=0x555100(/printers)
d [02/Jan/2018:13:46:14 +0100] cupsdIsAuthorized: level=CUPSD_AUTH_ANON, type=None, satisfy=CUPSD_AUTH_SATISFY_ALL, num_names=0
d [02/Jan/2018:13:46:14 +0100] cupsdIsAuthorized: auth=CUPSD_AUTH_ALLOW...
d [02/Jan/2018:13:46:14 +0100] POST /printers/lama
d [02/Jan/2018:13:46:14 +0100] CONTENT_TYPE = application/ipp
d [02/Jan/2018:13:46:14 +0100] cupsdReadClient: 10 con->data_encoding=HTTP_ENCODE_LENGTH, con->data_remaining=347, con->file=-1
E [02/Jan/2018:13:46:14 +0100] cupsdReadClient: 10 IPP Read Error!
D [02/Jan/2018:13:46:14 +0100] cupsdSendError: 10 code=400 (Bad Request)
D [02/Jan/2018:13:46:14 +0100] cupsdCloseClient: 10
d [02/Jan/2018:13:46:14 +0100] cupsdRemoveSelect: fd=10
d [02/Jan/2018:13:46:14 +0100] cupsdDoSelect: polling 6 fds for 1 seconds...
d [02/Jan/2018:13:46:15 +0100] cupsdDoSelect: epoll() returned 0...
d [02/Jan/2018:13:46:15 +0100] select_timeout(0): 100 seconds to timeout a client connection
d [02/Jan/2018:13:46:15 +0100] cupsdDoSelect: polling 6 fds for 100 seconds...