Log is attached. positive-deer.log.txt.zip
Why!??? .. all you had to do was share the URL the paste function generated (https://paste.libreelec.tv/positive-deer.log) which shows the filesystem on the USB drive was force-checked:
Apr 06 07:30:54.103762 LibreELEC kernel: scsi 4:0:0:0: Direct-Access USB SanDisk 3.2Gen1 1.00 PQ: 0 ANSI: 6
Apr 06 07:30:54.103925 LibreELEC kernel: sd 4:0:0:0: [sda] 60125184 512-byte logical blocks: (30.8 GB/28.7 GiB)
Apr 06 07:30:54.104039 LibreELEC kernel: sd 4:0:0:0: [sda] Write Protect is off
Apr 06 07:30:54.104150 LibreELEC kernel: sd 4:0:0:0: [sda] Mode Sense: 43 00 00 00
Apr 06 07:30:54.104263 LibreELEC kernel: sd 4:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Apr 06 07:30:54.104272 LibreELEC kernel: sda: sda1 sda2
Apr 06 07:30:54.104382 LibreELEC kernel: sd 4:0:0:0: [sda] Attached SCSI removable disk
Apr 06 07:30:54.104393 LibreELEC fsck: fsck.fat 4.2 (2021-01-31)
Apr 06 07:30:54.104405 LibreELEC fsck: /dev/sda1: 18 files, 44522/65501 clusters
Apr 06 07:30:54.104413 LibreELEC fsck: STORAGE contains a file system with errors, check forced.
Apr 06 07:30:54.104421 LibreELEC fsck: STORAGE: 36620/1847776 files (0.7% non-contiguous), 2185938/7383547 blocks
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but even with fsck there's loads of this:
Apr 06 07:30:55.157302 LibreELEC kernel: sd 4:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=DRIVER_OK cmd_age=0s
Apr 06 07:30:55.157923 LibreELEC kernel: sd 4:0:0:0: [sda] tag#0 Sense Key : 0x3 [current]
Apr 06 07:30:55.158357 LibreELEC kernel: sd 4:0:0:0: [sda] tag#0 ASC=0x11 ASCQ=0x0
Apr 06 07:30:55.158758 LibreELEC kernel: sd 4:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 02 11 42 88 00 00 08 00
Apr 06 07:30:55.159165 LibreELEC kernel: critical medium error, dev sda, sector 34685576 op 0x0:(READ) flags 0x3000 phys_seg 1 prio class 2
Apr 06 07:30:55.159217 LibreELEC kernel: EXT4-fs error (device sda2): __ext4_find_entry:1683: inode #1051944: comm mount-swap: reading directory lblock 0
And then:
Apr 06 07:31:07.955704 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1683: inode #1052028: comm kodi.bin: reading directory lblock 0
Apr 06 07:31:08.000646 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1694: inode #1052028: comm kodi.bin: checksumming directory block 0
Apr 06 07:31:10.457599 kodiLounge kernel: EXT4-fs error (device sda2): htree_dirblock_to_tree:1083: inode #1052028: comm kodi.bin: Directory block failed checksum
Apr 06 07:31:13.098569 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1694: inode #1052028: comm kodi.bin: checksumming directory block 0
Apr 06 07:31:13.191377 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1694: inode #1052028: comm kodi.bin: checksumming directory block 0
Apr 06 07:31:13.260223 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1694: inode #1052028: comm kodi.bin: checksumming directory block 0
Apr 06 07:31:13.308411 kodiLounge kernel: EXT4-fs error (device sda2): htree_dirblock_to_tree:1083: inode #1052028: comm kodi.bin: Directory block failed checksum
Apr 06 07:31:13.355379 kodiLounge kernel: EXT4-fs error (device sda2): __ext4_find_entry:1694: inode #1052028: comm kodi.bin: checksumming directory block 0
So the USB drive is bad (critical medium error) and this impacts data read from /dev/sda2 which is mounted as /storage. I think it is unlikely that the power outage caused the issue. It's more likely the drive went bad all on its own, but the outage results in unclean shutdown of the filesystem so the filesystem is in a 'dirty' state causing fsck to be run on boot, and this then finds or runs into the underlying media problem. On a memory device medium errors are failed cells in the flash memory chip that's inside.
I wouldn't waste time attempting to repair the USB drive as once cells start to fail the only outcome is more cells failing. If it's still possible (not guaranteed) you can backup the essential Kodi userdata like sources.xml, passwords.xml, DB files, and add-on settings files somewhere. Then make a clean install on a replacement USB drive, stop Kodi, and copy the userdata bits back.