While snooping around the stock init script, I spotted a variable, home, in the mountdata function standing out from the crowd. After doing some quick tests, the preliminary results are summarised as follows,
Prerequisite: The persistent overlay (.img, .aes or .inf) being on the same partition as the KNOPPIX file.
Functionality: Loading a specific persistent overlay at the boot time.
Usage: knoppix home=/mnt-system/foobar/dummy
*The dirname and basename cannot contain any whitespace characters.
*The basename needs to be unique if there are more than one overlay files in the same folder because the suffix cannot be part of the argument.
Gigabyte Aorus Ultra Durable B550 AORUS ELITE AX V2 Desktop Motherboard
$29.94
ASRock Z170M-ITX/ac LGA 1151 Intel Z170 HDMI USB 3.0 Mini ITX Intel Motherboard
$49.99
ASRock B550M Pro SE AM4 DDR4 SATA 6Gb/s 1 PCIe 4.0 x16 Micro ATX Motherboard
$84.99
MSI H81M-P33 Desktop Motherboard Intel MicroATX Socket LGA1150 USB 3.0 W/IO
$26.99
Gigabyte GA-Q170M-D3H-GSM LGA1151 DDR4 Desktop Motherboard (No I/O Plate)
$39.99
Asus Prime H310M-A R2.0 Intel LGA 1151 DDR4 Desktop Motherboard
$54.99
Asus H81M-C Intel LGA1150 DDR3 Desktop Motherboard MicroATX Socket H3
$23.99
Gigabyte Z370P D3 ATX Z370 LGA1151 Motherboard (Support Intel 6/7th 8th 9th)
$59.99
MSI PRO B650-P WiFi AMD AM5 DDR5 WiFi 6E ProSeries Motherboard
$107.30
Gigabyte GA-Q170M-D3H-GSM LGA1151 DDR4 Desktop Motherboard with I/O Plate
$49.99