Hey. Thanks. I managed to connect via serial. This is the last page of output:
[    4.263776] phy phy-10120000.usbphy.0: UTMI 16bit 30MHz
[    4.269118] ehci-platform 101c0000.ehci: EHCI Host Controller
[    4.274983] ehci-platform 101c0000.ehci: new USB bus registered, assigned bus number 1
[    4.283164] ehci-platform 101c0000.ehci: irq 26, io mem 0x101c0000
[    4.308675] ehci-platform 101c0000.ehci: USB 2.0 started, EHCI 1.00
[    4.316167] hub 1-0:1.0: USB hub found
[    4.320409] hub 1-0:1.0: 1 port detected
[    4.329459] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[    4.337382] ohci-platform: OHCI generic platform driver
[    4.343043] ohci-platform 101c1000.ohci: Generic Platform OHCI controller
[    4.350017] ohci-platform 101c1000.ohci: new USB bus registered, assigned bus number 2
[    4.358133] ohci-platform 101c1000.ohci: irq 26, io mem 0x101c1000
[    4.423797] hub 2-0:1.0: USB hub found
[    4.428044] hub 2-0:1.0: 1 port detected
[    4.445410] MTK MSDC device init.
[    4.488808] mtk-sd: MediaTek MT6575 MSDC Driver
[    4.496803] sdhci: Secure Digital Host Controller Interface driver
[    4.503152] sdhci: Copyright(c) Pierre Ossman
[    4.509064] sdhci-pltfm: SDHCI platform and OF driver helper
[    4.519467] usbcore: registered new interface driver usb-storage
[    4.529148] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    4.546978] init: - preinit -
[    5.389621] rt3050-esw 10110000.esw: link changed 0x00
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug[    5.589270] random: procd: uninitialized urandom read (4 bytes read, 10 bits of entropy available)
 level
[    8.436149] jffs2: notice: (396) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[    8.455942] mount_root: switching to jffs2 overlay
[    8.493035] urandom-seed: Seeding with /etc/urandom.seed
Error relocating /lib/libubus.so: uloop_cancelling: symbol not found
[    8.617476] watchdog watchdog0: watchdog did not stop!
[    8.622934] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
[    8.622934] 
[    8.633759] Rebooting in 1 seconds..
I remember seeing the Error relocating /lib/libubus.so: uloop_cancelling: symbol not found or something similar while I was doing some opkg upgrade ..., so presumably it's related to that.