You will not find your phone in the list of block devices because your phone does not present itself as a block device. HarmonyOS is based on Android 10. As far as I know, Android 10 only offers the Media Transfer Protocol (MTP). When the phone is configured to offer mtp, you will see it in the output of lsusb -v:
Device Descriptor:
iManufacturer 1 manufacturer
iProduct 2 phone
…
Configuration Descriptor:
iConfiguration 4 mtp_adb
…
You can access the files with any mtp client. I prefer mounting with gvfs-mtp, but any of the clients listed in https://wiki.archlinux.org/title/Media_Transfer_Protocol will do.