[Android Q&A, Help & Troubleshooting] 4bitFox:
fastboot getvar current-slot doesn't return anything

fastboot getvar all:

(bootloader) battery-soc-ok:yes
(bootloader) battery-voltage:4409
(bootloader) off-mode-charge:1
(bootloader) is-userspace:yes
(bootloader) partition-size:misc:0x100000
(bootloader) partition-size:uboot_bak:0x100000
(bootloader) partition-size:nr_fixnv2:0x800000
(bootloader) partition-size:databackup:0x3200000
(bootloader) partition-size:nr_agdsp:0x600000
(bootloader) partition-size:metadata:0x1000000
(bootloader) partition-size:nr_deltanv:0x200000
(bootloader) partition-size:nr_runtimenv1:0xA00000
(bootloader) partition-size:teecfg_bak:0x100000
(bootloader) partition-size:tpf:0x800000
(bootloader) partition-size:mmcblk0boot1:0x400000
(bootloader) partition-size:nr_nrphy:0x800000
(bootloader) partition-size:vbmeta_bak:0x100000
(bootloader) partition-size:nr_nrdsp2:0x500000
(bootloader) partition-size:nr_nrdsp1:0x500000
(bootloader) partition-size:logo:0x700000
(bootloader) partition-size:nr_sml:0x100000
(bootloader) partition-size:sysdumpdb:0xA00000
(bootloader) partition-size:prospecfg:0x100000
(bootloader) partition-size:uboot_log:0x400000
(bootloader) partition-size:nr_boot:0x2300000
(bootloader) partition-size:reserve:0xA00000
(bootloader) partition-size:wcnmodem:0xA00000
(bootloader) partition-size:nr_uboot:0x100000
(bootloader) partition-size:userdata:0x1A9BFFBE00
(bootloader) partition-size:uboot:0x100000
(bootloader) partition-size:miscdata:0x500000
(bootloader) partition-size:nr_modem:0x2800000
(bootloader) partition-size:mmcblk0boot0:0x400000
(bootloader) partition-size:nr_fixnv1:0x800000
(bootloader) partition-size:fbootlogo:0x700000
(bootloader) partition-size:teecfg:0x100000
(bootloader) partition-size:nr_pmsys:0x100000
(bootloader) partition-size:prodnv:0xA00000
(bootloader) partition-size:nr_spl:0x100000
(bootloader) partition-size:nr_runtimenv2:0xA00000
(bootloader) partition-size:trustos_bak:0x600000
(bootloader) partition-size:mmcblk0rpmb:0x1000000
(bootloader) partition-size:sml_bak:0x100000
(bootloader) partition-size:diag:0x100000
(bootloader) partition-size:nr_v3phy:0x800000
(bootloader) partition-size:trustos:0x600000
(bootloader) partition-size:vbmeta:0x100000
(bootloader) partition-size:vbmeta_system:0x100000
(bootloader) partition-size:dtbo:0x800000
(bootloader) partition-size:super:0x240000000
(bootloader) partition-size:recovery:0x2800000
(bootloader) partition-size:odmko:0x1900000
(bootloader) partition-size:boot:0x2300000
(bootloader) partition-size:vbmeta_vendor:0x100000
(bootloader) partition-size:socko:0x4B00000
(bootloader) partition-size:system:0x11D0D8000
(bootloader) partition-size:vendor:0x1F083000
(bootloader) partition-size:product:0x14227000
(bootloader) super-partition-name:super
(bootloader) partition-type:misc:raw
(bootloader) partition-type:uboot_bak:raw
(bootloader) partition-type:nr_fixnv2:raw
(bootloader) partition-type:databackup:raw
(bootloader) partition-type:nr_agdsp:raw
(bootloader) partition-type:metadata:raw
(bootloader) partition-type:nr_deltanv:raw
(bootloader) partition-type:nr_runtimenv1:raw
(bootloader) partition-type:teecfg_bak:raw
(bootloader) partition-type:tpf:raw
(bootloader) partition-type:mmcblk0boot1:raw
(bootloader) partition-type:nr_nrphy:raw
(bootloader) partition-type:vbmeta_bak:raw
(bootloader) partition-type:nr_nrdsp2:raw
(bootloader) partition-type:nr_nrdsp1:raw
(bootloader) partition-type:logo:raw
(bootloader) partition-type:nr_sml:raw
(bootloader) partition-type:sysdumpdb:raw
(bootloader) partition-type:prospecfg:raw
(bootloader) partition-type:uboot_log:raw
(bootloader) partition-type:nr_boot:raw
(bootloader) partition-type:reserve:raw
(bootloader) partition-type:wcnmodem:raw
(bootloader) partition-type:nr_uboot:raw
(bootloader) partition-type:userdata:f2fs
(bootloader) partition-type:uboot:raw
(bootloader) partition-type:miscdata:raw
(bootloader) partition-type:nr_modem:raw
(bootloader) partition-type:mmcblk0boot0:raw
(bootloader) partition-type:nr_fixnv1:raw
(bootloader) partition-type:fbootlogo:raw
(bootloader) partition-type:teecfg:raw
(bootloader) partition-type:nr_pmsys:raw
(bootloader) partition-type:prodnv:ext4
(bootloader) partition-type:nr_spl:raw
(bootloader) partition-type:nr_runtimenv2:raw
(bootloader) partition-type:trustos_bak:raw
(bootloader) partition-type:mmcblk0rpmb:raw
(bootloader) partition-type:sml_bak:raw
(bootloader) partition-type:diag:raw
(bootloader) partition-type:nr_v3phy:raw
(bootloader) partition-type:cache:ext4
(bootloader) partition-type:trustos:raw
(bootloader) partition-type:mmcblk0:raw
(bootloader) partition-type:vbmeta:raw
(bootloader) partition-type:vbmeta_system:raw
(bootloader) partition-type:dtbo:raw
(bootloader) partition-type:super:raw
(bootloader) partition-type:recovery:raw
(bootloader) partition-type:odmko:ext4
(bootloader) partition-type:boot:raw
(bootloader) partition-type:vbmeta_vendor:raw
(bootloader) partition-type:socko:ext4
(bootloader) partition-type:system:raw
(bootloader) partition-type:vendor:raw
(bootloader) partition-type:product:ext4
(bootloader) has-slot:misc:no
(bootloader) has-slot:uboot_bak:no
(bootloader) has-slot:nr_fixnv2:no
(bootloader) has-slot:databackup:no
(bootloader) has-slot:nr_agdsp:no
(bootloader) has-slot:metadata:no
(bootloader) has-slot:nr_deltanv:no
(bootloader) has-slot:nr_runtimenv1:no
(bootloader) has-slot:teecfg_bak:no
(bootloader) has-slot:tpf:no
(bootloader) has-slot:mmcblk0boot1:no
(bootloader) has-slot:nr_nrphy:no
(bootloader) has-slot:vbmeta_bak:no
(bootloader) has-slot:nr_nrdsp2:no
(bootloader) has-slot:nr_nrdsp1:no
(bootloader) has-slot:logo:no
(bootloader) has-slot:nr_sml:no
(bootloader) has-slot:sysdumpdb:no
(bootloader) has-slot:prospecfg:no
(bootloader) has-slot:uboot_log:no
(bootloader) has-slot:nr_boot:no
(bootloader) has-slot:reserve:no
(bootloader) has-slot:wcnmodem:no
(bootloader) has-slot:nr_uboot:no
(bootloader) has-slot:userdata:no
(bootloader) has-slot:uboot:no
(bootloader) has-slot:miscdata:no
(bootloader) has-slot:nr_modem:no
(bootloader) has-slot:mmcblk0boot0:no
(bootloader) has-slot:nr_fixnv1:no
(bootloader) has-slot:fbootlogo:no
(bootloader) has-slot:teecfg:no
(bootloader) has-slot:nr_pmsys:no
(bootloader) has-slot:prodnv:no
(bootloader) has-slot:nr_spl:no
(bootloader) has-slot:nr_runtimenv2:no
(bootloader) has-slot:trustos_bak:no
(bootloader) has-slot:mmcblk0rpmb:no
(bootloader) has-slot:sml_bak:no
(bootloader) has-slot:diag:no
(bootloader) has-slot:nr_v3phy:no
(bootloader) has-slot:cache:no
(bootloader) has-slot:gnssmodem:no
(bootloader) has-slot:trustos:no
(bootloader) has-slot:mmcblk0:no
(bootloader) has-slot:vbmeta:no
(bootloader) has-slot:l_pmsys:no
(bootloader) has-slot:vbmeta_system:no
(bootloader) has-slot:dtbo:no
(bootloader) has-slot:super:no
(bootloader) has-slot:recovery:no
(bootloader) has-slot:odmko:no
(bootloader) has-slot:boot:no
(bootloader) has-slot:l_agdsp:no
(bootloader) has-slot:vbmeta_vendor:no
(bootloader) has-slot:socko:no
(bootloader) has-slot:system:no
(bootloader) has-slot:vendor:no
(bootloader) has-slot:product:no
(bootloader) max-download-size:0x20000000
(bootloader) version-baseband:
(bootloader) slot-count:0
(bootloader) is-logical:misc:no
(bootloader) is-logical:uboot_bak:no
(bootloader) is-logical:nr_fixnv2:no
(bootloader) is-logical:databackup:no
(bootloader) is-logical:nr_agdsp:no
(bootloader) is-logical:metadata:no
(bootloader) is-logical:nr_deltanv:no
(bootloader) is-logical:nr_runtimenv1:no
(bootloader) is-logical:teecfg_bak:no
(bootloader) is-logical:tpf:no
(bootloader) is-logical:mmcblk0boot1:no
(bootloader) is-logical:nr_nrphy:no
(bootloader) is-logical:vbmeta_bak:no
(bootloader) is-logical:nr_nrdsp2:no
(bootloader) is-logical:nr_nrdsp1:no
(bootloader) is-logical:logo:no
(bootloader) is-logical:nr_sml:no
(bootloader) is-logical:sysdumpdb:no
(bootloader) is-logical:prospecfg:no
(bootloader) is-logical:uboot_log:no
(bootloader) is-logical:nr_boot:no
(bootloader) is-logical:reserve:no
(bootloader) is-logical:wcnmodem:no
(bootloader) is-logical:nr_uboot:no
(bootloader) is-logical:userdata:no
(bootloader) is-logical:uboot:no
(bootloader) is-logical:miscdata:no
(bootloader) is-logical:nr_modem:no
(bootloader) is-logical:mmcblk0boot0:no
(bootloader) is-logical:nr_fixnv1:no
(bootloader) is-logical:fbootlogo:no
(bootloader) is-logical:teecfg:no
(bootloader) is-logical:nr_pmsys:no
(bootloader) is-logical:prodnv:no
(bootloader) is-logical:nr_spl:no
(bootloader) is-logical:nr_runtimenv2:no
(bootloader) is-logical:trustos_bak:no
(bootloader) is-logical:mmcblk0rpmb:no
(bootloader) is-logical:sml_bak:no
(bootloader) is-logical:diag:no
(bootloader) is-logical:nr_v3phy:no
(bootloader) is-logical:cache:no
(bootloader) is-logical:trustos:no
(bootloader) is-logical:mmcblk0:no
(bootloader) is-logical:vbmeta:no
(bootloader) is-logical:vbmeta_system:no
(bootloader) is-logical:dtbo:no
(bootloader) is-logical:super:no
(bootloader) is-logical:recovery:no
(bootloader) is-logical:odmko:no
(bootloader) is-logical:boot:no
(bootloader) is-logical:vbmeta_vendor:no
(bootloader) is-logical:socko:no
(bootloader) is-logical:system:yes
(bootloader) is-logical:vendor:yes
(bootloader) is-logical:product:yes
(bootloader) secure:yes
(bootloader) variant:Unisoc
(bootloader) hw-revision:0
(bootloader) product:HNR320T
(bootloader) current-slot:
(bootloader) version-bootloader:unknown
(bootloader) unlocked:yes
(bootloader) version:0.4