As someone who has some experience compiling kernels, I think in general supporting custom kernels is beyond the scope of Ask Ubuntu.
Perhaps on other stack exchange sites, I am not sure.
The reasons are:
As far as I know, the Ubuntu kernel team does not support custom kernels.
The Ubuntu documentation clearly states custom kernels are not supported.
Compiling a custom kernel involves a configuration file with 6, 000 lines of options, let alone actually modifying the underlying C code. Many of these options are hardware dependent and the Ubuntu Kernel team already releases a kernel that is already very generic.
Actual kernel bugs, if they exist in the code, are reported to kernel.org. The Ubuntu kernel team supports only a minor portion of the code, such as apparmor.
As with all rules, there may be some exceptions such as applying a patch or perhaps a trivial configuration change, that could be considered on a case-by-case basis.
In summary, in general, IMO custom kernels are highly specialized and it is easy to break, and hard to fix a kernel.config
