I have also tried to use a different kernel than what is in the original iso using ubuntu 18.04 and linux mint 19 images. My new kernel is compiled using "make deb-pkg" and installed in cubic root using dpkg -i linux*.deb. This kernel works just fine on my linux mint 19, ubuntu 18 and Arch Linux installs. The packages installs just fine except a warning that can not determine root from fstab file. When I click next after making all of my changes in the chroot it exits chroot enviorment and nothing happens after pressing next button. If I click the back button and choose Create a disk image button and click the next button cubic just hangs and does nothing.

Get vmlinuz version from file type..... /home/ubuntu/image/squashfs-        
                                            root/boot/vmlinuz-4.18.0-rc2-udl+   
    Execute synchronously.................. file "/home/ubuntu/image/squashfs-  
                                            root/boot/vmlinuz-4.18.0-rc2-udl+"  
    No processes were found that are    
    using directory........................ /home/ubuntu/image/squashfs-root    
    Get mount points in directory.......... /home/ubuntu/image/squashfs-root    
    Execute synchronously.................. mount                               
    Get vmlinuz version from file       
    contents............................... /home/ubuntu/image/squashfs-        
                                            root/boot/vmlinuz-4.18.0-rc2-udl+   
    Set a new process for thread id........ 140620711057152                     
    The new process id is.................. 10504                               
    No mount points were found in.......... /home/ubuntu/image/squashfs-root    
    Finished running thread with id........ 140620711057152                     
    Exception encountered in thread........ 140620413097728                     
    Ignore exception?...................... No                                  
    The tracekback is...................... Traceback (most recent call last):  
                                            File                                
                                            "/usr/share/cubic/transition.py",   
                                            line 95, in run     self.action()   
                                            File                                
                                            "/usr/share/cubic/transition.py",   
                                            line 400, in action     self)   File
                                            "/usr/share/cubic/transitions.py",  
                                            line 2564, in transition__from__term
                                            inal_page__to__manage_options_page  
                                            directory_2)   File                 
                                            "/usr/share/cubic/utilities.py",    
                                            line 2072, in                       
                                            create_vmlinuz_version_details_list 
                                            get_vmlinuz_versions_list_from_direc
                                            tory(directory))   File             
                                            "/usr/share/cubic/utilities.py",    
                                            line 2167, in get_vmlinuz_versions_l
                                            ist_from_directory                  
                                            version_integers = tuple(map(int,   
                                            re.split('[.-]', version_name)))    
                                            File "/usr/lib/python3.6/re.py",    
                                            line 212, in split     return       
                                            _compile(pattern,                   
                                            flags).split(string, maxsplit)      
                                            TypeError: expected string or bytes-
                                            like object                         
    Finished running thread with id........ 140620413097728