Hey Benny!   
      
    BP> only 6.4.0 here on gentoo is stable   
      
   I haven't used that version in awhile.  My best guess is that it is perfectly   
   fine.   
      
    BP> i dont know why older kernels stopped building firmware   
      
   There is little need to rebuild firmware unless of course you are adding new   
   hardware that requires newer firmware.  If that is the case then the older   
   kernel's in-tree firmware is unlikely to resolve that issue.  All of the   
   firmware I currently require is supplied by linux-firmware.git instead so it   
   is of no consequence that it is no longer supplied by the newer kernels   
   especially considering none of it was ever used in my particular situation.    
   Exactly what firmware did you need to build with every kernel upgrade?  I bet   
   very little, if any, has changed as far as firmware is concerned especially   
   regarding an i686 based system.   
      
    BP> have it build in kernel makes sure its tested and works with the   
    BP> kernel version   
      
   For example?  The newest update here was on Nov. 26, 2017 (htc_9271-1.4.0.fw)   
   and was never supplied by the in-tree kernel's firmware.  It was always   
   maintained by linux-firmware.git.  So far I've never needed to obtain firmware   
   from any other source ... thank goodness.   
      
   Life is good,   
   Maurice   
      
   ... Don't cry for me I have vi.   
   --- GNU bash, version 4.4.19(1)-release (x86_64-silvermont-linux-gnu)   
    * Origin: Little Mikey's Brain - Ladysmith BC, Canada (1:153/7001)