For several years I have run both the Knoppix ISO-image and disk-based versions under kvm for installs, maintenance etc. The basic method works for 8.3 too, but only as far as the first flash install.
Klaus K has made Knoppix more "fool-proof" to run under kvm by restricting it to read-only mode. For many users, that is clearly a feature: You may run your ordinary Knoppix install under kvm so it functions as both host and guest at once, but if persistent store is involved, and the host and the guest instances perform different updates to that, then what?
It is only a question of time until the file system is corrupted - it is easy to imagine that prof. Knopper has introduced this restriction from experiences with broken systems.
The bug is that it doesn't stop there. If you run different copies of Knoppix on different partitions, or run Knoppix under another OS variety, even another version of Knoppix, the only thing to be careful about is that the partition where the persistent store of the VM resides is not writable by other OS'es. But don't try to explain that to Knoppix 8.3. It only checks whether it is run under kvm, and in that case, the system is mounted read-only. Which kind of blocks many important uses of Knoppix images.
While the default behaviour is "correct", there must be a cheatcode for disabling it, e.g. VIRTWRITE. I guess specialists on minirt.gz should not have too much problems rolling their own, but this is a general issue, so for me it belongs in Knopper-land proper.
Lenovo LOQ Laptop, i7-13700H, GB, Up to 1TB SSD, Up To Win 11 Pro
$701.09
Lenovo Ideapad 1 15Iau7 15.6" Laptop Intel Core i5-1235U 8GB RAM 512GB SSD W11P
$299.99
Lenovo ThinkPad E, AMD, 8GB RAM, 256GB SSD, No OS, 20T80005US
$280.00
Lenovo ThinkBook 15 Gen 4 Notebook 15.6" FHD AMD R7 5825U 16GB RAM 512GB SSD
$479.99
Lenovo ThinkBook 15 Gen 4 Notebook 15.6" FHD Intel Core i7-1255U 8GB RAM
$514.99
Lenovo LOQ 15.6" FHD 144Hz Gaming Laptop i5-12450HX 12GB RAM 512GB SSD RTX 3050
$599.99
Lenovo Ideapad 1i 15.6" FHD Touchscreen Laptop - Intel Core i3-1215U with 8GB...
$279.99
Lenovo IdeaPad Gaming 3 15.6'' (256GB SSD AMD Ryzen 5 6600H 3.3GHz 8GB RAM)...
$229.00
Lenovo ThinkPad Yoga Touchscreen Laptop PC 11.6" Windows 10 4GB RAM 256GB SSD
$89.99
Lenovo ThinkPad 11e 11.6" Laptop Intel Core m3 8GB RAM 128GB SSD Windows 10
$59.99