[Galaxy Note 3 Android Development] stefanct:
Some progress: I have built a ghetto USB UART jig and was able to obtain a startup log of a failing boot. I forgot which image I flashed last but it doesn't matter too much atm... here is the important part at the end:

[ 25.220441] samsung_dsi_panel_event_handler : unknown event
[ 25.233592] mdss_dsi_isr: ndx=0 isr=3200202
[ 25.236838] mdss_dsi_isr: isr[0]=3200202 1000000
[ 25.241334] mdss_dsi_dln0_phy_err: status=98888
[ 25.246232] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.250089] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.254589] mdss_dsi_dln0_phy_err: status=98888
[ 25.263118] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.266401] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.270770] mdss_dsi_dln0_phy_err: status=98888
[ 25.279690] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.282969] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.287351] mdss_dsi_dln0_phy_err: status=98888
[ 25.293219] mipi_samsung_disp_send_cmd : cmd_size is zero!..
[ 25.312686] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.315905] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.320406] mdss_dsi_dln0_phy_err: status=98888
[ 25.333835] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.337118] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.341491] mdss_dsi_dln0_phy_err: status=98888
[ 25.354005] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.357284] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.361663] mdss_dsi_dln0_phy_err: status=98888
[ 25.374213] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.377428] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.381868] mdss_dsi_dln0_phy_err: status=98888
[ 25.394393] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.397610] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.402113] mdss_dsi_dln0_phy_err: status=98888
[ 25.411355] mipi_samsung_disp_send_cmd : cmd_size is zero!..
[ 25.430845] mdss_dsi_isr: ndx=0 isr=3300203
[ 25.434128] mdss_dsi_isr: isr[0]=3300203 1000000
[ 25.438499] mdss_dsi_dln0_phy_err: status=98888
[ 25.444047] Error reading LCD NV data !!!!
[ 25.451247] mdss_dsi_panel_dimming_init:ldi_fps register otp value read fail = 0x73
[ 25.458032] Kernel panic - not syncing: LDI FPS Register OTP Value Read Fail
[ 25.464979] [<c010cc18>] (unwind_backtrace+0x0/0x138) from [<c0b35394>] (panic+0xb4/0x238)
[ 25.473287] [<c0b35394>] (panic+0xb4/0x238) from [<c0467960>] (mdss_dsi_panel_dimming_init+0x17c/0x4e4)
[ 25.482658] [<c0467960>] (mdss_dsi_panel_dimming_init+0x17c/0x4e4) from [<c0467dc0>] (mdss_dsi_panel_on+0xf8/0x250)
[ 25.493076] [<c0467dc0>] (mdss_dsi_panel_on+0xf8/0x250) from [<c045b150>] (mdss_dsi_unblank+0x7c/0x144)
[ 25.502446] [<c045b150>] (mdss_dsi_unblank+0x7c/0x144) from [<c045d22c>] (mdss_dsi_event_handler+0x178/0xa84)
[ 25.512281] [<c045d22c>] (mdss_dsi_event_handler+0x178/0xa84) from [<c0432d98>] (mdss_mdp_ctl_intf_event+0x80/0xb8)
[ 25.522759] [<c0432d98>] (mdss_mdp_ctl_intf_event+0x80/0xb8) from [<c0449ec0>] (mdss_mdp_cmd_kickoff+0x188/0x6c4)
[ 25.533003] [<c0449ec0>] (mdss_mdp_cmd_kickoff+0x188/0x6c4) from [<c043500c>] (mdss_mdp_display_commit+0xb5c/0xd68)
[ 25.543420] [<c043500c>] (mdss_mdp_display_commit+0xb5c/0xd68) from [<c0451734>] (mdss_mdp_overlay_kickoff+0x5fc/0xb30)
[ 25.554186] [<c0451734>] (mdss_mdp_overlay_kickoff+0x5fc/0xb30) from [<c048b664>] (__mdss_fb_display_thread+0x1e8/0x4c4)
[ 25.565038] [<c048b664>] (__mdss_fb_display_thread+0x1e8/0x4c4) from [<c01cc498>] (kthread+0x88/0x94)

As you can see the reason is indeed related to the display. It looks to me as if it tries to read some ID or calibration data a few times and then gives up. Unfortunately, I was not able to find a stock version that provokes the same behavior: all stock images since ATO-N9005XXUENC2-20140403173244 (android 4.4.2) work fine with the new display and the next older one (ATO-N9005XXUDMJ7-20131111165854) can't be flashed ("sw rev check fail : [aboot]Fused 3 > binary 2"). Possibly they disabled downgrade for exactly that reason...?

Anyway, I'd be thankful for any ideas how to continue. I have downloaded the source of the latest (lollipop) stock kernel (based on 3.4.0) and would (like to) compare it with a version that does not work... but which version should I compare it to? The ones currently used by any custom rom or twrp would be very different and a PITA to compare/analyze I presume...

The least I can do is to flash the 5.0 stock and post a good log...