Back from holidays I did a rebbot of LE (12.2.) and TVHeadend 4.3 and scanded dmesg for tuner related messages (see below)
<[ 9.923347] em28xx 1-1.3:1.0: New device HCW soloHD @ 480 Mbps (2040:8268, interface 0, class 0)
[ 9.923383] em28xx 1-1.3:1.0: DVB interface 0 found: bulk
[ 9.975901] em28xx 1-1.3:1.0: chip ID is em28178
[ 11.979847] em28xx 1-1.3:1.0: EEPROM ID = 26 00 01 00, EEPROM hash = 0x4bcfcb80
[ 11.979877] em28xx 1-1.3:1.0: EEPROM info:
[ 11.979884] em28xx 1-1.3:1.0: microcode start address = 0x0004, boot configuration = 0x01
[ 11.988579] em28xx 1-1.3:1.0: AC97 audio (5 sample rates)
[ 11.988611] em28xx 1-1.3:1.0: 500mA max power
[ 11.988619] em28xx 1-1.3:1.0: Table at offset 0x27, strings=0x0e6a, 0x1888, 0x087e
[ 12.045246] em28xx 1-1.3:1.0: Identified as PCTV tripleStick (292e) (card=94)
[ 12.045294] em28xx 1-1.3:1.0: dvb set to bulk mode.
[ 12.045949] usbcore: registered new interface driver em28xx
[ 12.210632] em28xx 1-1.3:1.0: Binding DVB extension
[ 12.453306] em28xx 1-1.3:1.0: DVB: registering adapter 0 frontend 0 (Silicon Labs Si2168)...
[ 12.472248] em28xx 1-1.3:1.0: DVB extension successfully initialized
[ 12.472318] em28xx: Registered (Em28xx dvb Extension) extension
[ 12.552306] em28xx 1-1.3:1.0: Registering input extension
[ 12.691142] rc rc0: lirc_dev: driver em28xx registered at minor = 0, scancode receiver, no transmitter
[ 12.693483] em28xx 1-1.3:1.0: Input extension successfully initialized
[ 12.693512] em28xx: Registered (Em28xx Input Extension) extension
[ 15.902190] em28xx 1-1.3:1.0: DVB: adapter 0 frontend 0 frequency 0 out of range (48000000..870000000)>
The last line is strange because the USB tuner worked well in the past (up to LE 12.0.2 and TVH 4.2) and all channels are on 366MHz. A manually added MUX shows Original Network ID 65536 which I didn't enter. The correct Network ID should be 43168.
If the problem is caused by the USB tuner (Hauppage-soloHD), I'm willing to buy a new, working one. Any recommendations?