I saved both system log and kernel log from within LuCI.
System log: https://pastebin.com/SmQtMfum
Kernel log: https://pastebin.com/Zva49nyt
Device: TP-Link Archer A6 v3
OpenWrt version: 21.02.2 (upgrade from snapshot 02/15/2022, followed by soft reset from failsafe mode)
Issue: Upgrading seemed to brick my router (with configuration preserved, including 5 GHz WiFi enabled). After soft resetting through failsafe mode, enabling 5 GHz WiFi through LuCI fails and it makes the router reboot with 5 GHz WiFi setting reverted (disabled again). Enabling 2.4 GHz WiFi seems to work.