I've never seen this before, I see disk0, disk3. & disk4, but no disk1 or disk2 ???
Here's mine without backup drives attached...
/dev/disk0 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_APFS Container disk4 1000.0 GB disk0s2
/dev/disk1 (external):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme 1.9 TB disk1
1: EFI 209.7 MB disk1s1
2: Apple_APFS Container disk5 1.9 TB disk1s2
/dev/disk2 (external):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme 1.9 TB disk2
1: EFI EFI 314.6 MB disk2s1
2: Apple_HFS SSD2 1.9 TB disk2s2
/dev/disk3 (internal):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme 28.0 GB disk3
1: EFI EFI 314.6 MB disk3s1
2: Apple_APFS Container disk4 27.6 GB disk3s2
/dev/disk4 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +1.0 TB disk4
Physical Stores disk3s2, disk0s2
1: APFS Volume Macintosh HD 11.3 GB disk4s1
2: APFS Volume Macintosh HD - Data 653.7 GB disk4s2
3: APFS Volume Preboot 84.5 MB disk4s3
4: APFS Volume Recovery 529.0 MB disk4s4
5: APFS Volume VM 2.1 GB disk4s5
/dev/disk5 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +1.9 TB disk5
Physical Store disk1s2
1: APFS Volume SSD3 - Data 1.1 TB disk5s1
2: APFS Volume Preboot 316.8 MB disk5s2
3: APFS Volume Recovery 622.9 MB disk5s3
4: APFS Volume VM 17.2 GB disk5s4
5: APFS Volume 15.3 GB disk5s5
6: APFS Volume Update 786.4 KB disk5s6