[OnePlus 7T Pro (Regular & McLaren) Guides, News...] TEKHD:
How to backup your own partitions before messing with the phone:

Partition Structure on OnePlus 7T Pro 5G McLaren Edition:

ls -al /dev/block/platform/soc/1d84000.ufshc/by-name

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 5gdump -> /dev/block/sda21

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 ALIGN_TO_128K_1 -> /dev/block/sdd1

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 ALIGN_TO_128K_2 -> /dev/block/sdf1

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 LOGO_a -> /dev/block/sde21

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 LOGO_b -> /dev/block/sde47

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 abl_a -> /dev/block/sde8

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 abl_b -> /dev/block/sde35

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 aging -> /dev/block/sde54

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 aging_mod -> /dev/block/sde55

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 aop_a -> /dev/block/sde1

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 aop_b -> /dev/block/sde28

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 apdp -> /dev/block/sde59

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 bluetooth_a -> /dev/block/sde5

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 bluetooth_b -> /dev/block/sde32

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 boot_a -> /dev/block/sde11

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 boot_b -> /dev/block/sde38

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 carrier -> /dev/block/sda18

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 catecontentfv -> /dev/block/sde72

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 catefv -> /dev/block/sde71

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 cateloader -> /dev/block/sde66

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 cdt -> /dev/block/sdd2

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 cmnlib64_a -> /dev/block/sde13

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 cmnlib64_b -> /dev/block/sde40

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 cmnlib_a -> /dev/block/sde12

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 cmnlib_b -> /dev/block/sde39

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 config -> /dev/block/sda12

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 core_nhlos -> /dev/block/sde20

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 ddr -> /dev/block/sdd3

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 devcfg_a -> /dev/block/sde14

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 devcfg_b -> /dev/block/sde41

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 devinfo -> /dev/block/sde57

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 dip -> /dev/block/sde58

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 dsp_a -> /dev/block/sde9

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 dsp_b -> /dev/block/sde36

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 dtbo_a -> /dev/block/sde17

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 dtbo_b -> /dev/block/sde44

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 frp -> /dev/block/sda6

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 fsc -> /dev/block/sdf5

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 fsg -> /dev/block/sdf4

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs1_a -> /dev/block/sde22

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs1_b -> /dev/block/sde48

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs2_a -> /dev/block/sde23

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs2_b -> /dev/block/sde49

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs3_a -> /dev/block/sde24

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs3_b -> /dev/block/sde50

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs4_a -> /dev/block/sde25

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs4_b -> /dev/block/sde51

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs5_a -> /dev/block/sde26

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 fw_ufs5_b -> /dev/block/sde52

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 hyp_a -> /dev/block/sde3

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 hyp_b -> /dev/block/sde30

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 imagefv_a -> /dev/block/sde19

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 imagefv_b -> /dev/block/sde46

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 keymaster_a -> /dev/block/sde10

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 keymaster_b -> /dev/block/sde37

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 keystore -> /dev/block/sda5

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 limits -> /dev/block/sde63

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 logdump -> /dev/block/sde67

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 logfs -> /dev/block/sde65

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdm1m9kefs1 -> /dev/block/sdf7

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdm1m9kefs2 -> /dev/block/sdf8

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdm1m9kefs3 -> /dev/block/sdf6

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdm1m9kefsc -> /dev/block/sdf9

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 mdm1oemnvbktmp -> /dev/block/sde77

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 mdm_oem_dycnvbk -> /dev/block/sda10

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 mdm_oem_stanvbk -> /dev/block/sda11

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdmddr -> /dev/block/sdd4

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdtp_a -> /dev/block/sde7

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 mdtp_b -> /dev/block/sde34

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 mdtpsecapp_a -> /dev/block/sde6

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 mdtpsecapp_b -> /dev/block/sde33

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 metadata -> /dev/block/sda19

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 misc -> /dev/block/sda3

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 modem_a -> /dev/block/sde4

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 modem_b -> /dev/block/sde31

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 modemst1 -> /dev/block/sdf2

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 modemst2 -> /dev/block/sdf3

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 msadp -> /dev/block/sde60

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 multiimgoem_a -> /dev/block/sde27

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 multiimgoem_b -> /dev/block/sde53

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 oem_dycnvbk -> /dev/block/sda8

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 oem_stanvbk -> /dev/block/sda9

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 op1 -> /dev/block/sde56

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 op2 -> /dev/block/sda7

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 param -> /dev/block/sda4

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 persist -> /dev/block/sda2

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 qupfw_a -> /dev/block/sde15

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 qupfw_b -> /dev/block/sde42

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 rawdump -> /dev/block/sda20

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 recovery_a -> /dev/block/sda14

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 recovery_b -> /dev/block/sda15

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 reserve1 -> /dev/block/sde73

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 reserve2 -> /dev/block/sde74

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 reserve3 -> /dev/block/sde75

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 reserve4 -> /dev/block/sde76

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 secdata -> /dev/block/sde70

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 splash -> /dev/block/sde62

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 spunvm -> /dev/block/sde61

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 ssd -> /dev/block/sda1

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 storsec_a -> /dev/block/sde68

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 storsec_b -> /dev/block/sde78

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 super -> /dev/block/sda13

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 toolsfv -> /dev/block/sde64

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 tz_a -> /dev/block/sde2

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 tz_b -> /dev/block/sde29

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 uefisecapp_a -> /dev/block/sde18

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 uefisecapp_b -> /dev/block/sde45

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 uefivarstore -> /dev/block/sde69

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 userdata -> /dev/block/sda22

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 vbmeta_a -> /dev/block/sde16

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 vbmeta_b -> /dev/block/sde43

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 vbmeta_system_a -> /dev/block/sda16

lrwxrwxrwx 1 root root 16 1970-01-29 11:39 vbmeta_system_b -> /dev/block/sda17

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 xbl_a -> /dev/block/sdb1

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 xbl_b -> /dev/block/sdc1

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 xbl_config_a -> /dev/block/sdb2

lrwxrwxrwx 1 root root 15 1970-01-29 11:39 xbl_config_b -> /dev/block/sdc2

Boot into Fastboot ->

adb reboot fastboot

Run TWRP -> (You need to have twrp.img on your ADB folder)

fastboot boot ./twrp.img

For example, if you want to backup LOGO_a ->

adb pull /dev/block/sde21 LOGO_a.img

After you are done, simply exit/reboot from TWRP (with no modifications, read only)

or

adb reboot

Done

Automatic Extraction Tool for TMO 5G McLaren available here.