Did you try enabling IPv6 from the command line when you launch TVH?
#tvheadend --ipv6
# ./tvheadend --help
Usage: ./tvheadend [OPTIONS]
Generic options
-h, --help Show this page
-v, --version Show version information
Service configuration
-c, --config Alternate configuration path
-B, --nobackup Don't backup configuration tree at upgrade
-f, --fork Fork and run as daemon
-u, --user Run as user
-g, --group Run as group
-p, --pid Alternate PID path
-C, --firstrun If no user account exists then create one with
no username and no password. Use with care as
it will allow world-wide administrative access
to your Tvheadend installation until you create or edit
the access control from within the Tvheadend web interface.
-a, --adapters Only use specified DVB adapters (comma-separated, -1 = none)
--satip_bindaddr Specify bind address for SAT>IP server
--satip_rtsp SAT>IP RTSP port number for server
(default: -1 = disable, 0 = webconfig, standard port is 554)
--nosatip Disable SAT>IP client
--satip_xml URL with the SAT>IP server XML location
Server connectivity
-6, --ipv6 Listen on IPv6
-b, --bindaddr Specify bind address
--http_port Specify alternative http port
--http_root Specify alternative http webroot
--htsp_port Specify alternative htsp port
--htsp_port2 Specify extra htsp port
--useragent Specify User-Agent header for the http client
--xspf Use XSPF playlist instead of M3U
Debug options
-d, --stderr Enable debug on stderr
-n, --nostderr Disable debug on stderr
-s, --syslog Enable debug to syslog
-S, --nosyslog Disable syslog (all messages)
-l, --logfile Enable debug to file
--debug Enable debug subsystems
--trace Enable trace subsystems
--subsystems List subsystems
--fileline Add file and line numbers to debug
--threadid Add the thread ID to debug
--libav More verbose libav log
--uidebug Enable web UI debug (non-minified JS)
-A, --abort Immediately abort
-D, --dump Enable coredumps for daemon
--noacl Disable all access control checks
--nobat Disable DVB bouquets
-j, --join Subscribe to a service permanently
Testing options
--tsfile_tuners Number of tsfile tuners
--tsfile tsfile input (mux file)
--tprofile Gather timing statistics for the code
--thrdebug Thread debugging
