Per IRC discussion with vorlon on 2022-03-25.
Ubuntu Studio's squashfs file size is reaching and exceeding the 4096MB file size limited by ISO 9660. However, it has been discovered that xorriso is capable of creating an image with file sized greater than this, per the manpage:
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Level 3 allows ISO names with up to 32 characters and file size of up to 400 GiB - 200 KiB. (This size limitation is set by the xorriso implementation and not by ISO 9660 which would allow nearly 8 TiB.)
'''
Ubuntu 22.04 is certainly running a new enough kernel to do-away with the file size limitations previously imposed. For Ubuntu Studio, we have decided that burning a physical DVD is no longer within the scope as USB sticks are plentiful and relatively inexpensive when the correct file size for our images, which aren't exceeding 5GB. Therefore, an entry of "-iso-level 3" added to the xorisso command when building the images could help rectify this now-outdated file size limit.
Unfortunately the proposed patch doesn't work because we invoke xorriso -as mkisofs, which is incompatible with -file_size_limit. So this is only possible if the rest of the options are mapped to xorriso instead of mkisofs (assuming they ARE all mappable).