native-comp - Questions: eln-cache and subdirs.el?

[Arthur Miller]

I have something like 3 different eln-caches now
  
  28.0.50-x86_64-pc-linux-gnu-8e48a483af0cc5adcb56147eb760a39f
  2020-09-27 12:03 28.0.50-x86_64-pc-linux-gnu-cfb9403e84a6e99e5ac1bea6ab4abade
  2020-08-21 17:21 x86_64-pc-linux-gnu-958646d5fbcc566c

Are they all used or I can delete some? I also see that not all files
are in all folders;

About subdirs:

since Emacs deprecated subdirs; are there plans to get rid of that
mechanism later on, or it is it here to stay? I see in source code that
content of all subidirs.el is same (I checked few) on my machine; it
says:

;; In load-path, after this directory should come
;; certain of its subdirectories.  Here we specify them.
(normal-top-level-add-to-load-path '("eln-x86_64-pc-linux-gnu-600a7a2b93bc09d0" 
))
;; Local Variables:
;; version-control: never
;; no-byte-compile: t
;; no-update-autoloads: t
;; End:

Since Emacs screams about deprecation when compiling; maybe this could
be saved into 'somefile.el' and then followed by a directory listing, or
just as assoc list?

Example:

;; In load-path, after this directory should come
;; certain of its subdirectories.  Here we specify them.
;; Local Variables:
;; version-control: never
;; no-byte-compile: t
;; no-update-autoloads: t
;; End:
((dir1 . '(normal-top-level-add-to-load-path 
"eln-x86_64-pc-linux-gnu-600a7a2b93bc09d0" ))
 (dir2 . '(normal-top-level-add-to-load-path 
"eln-x86_64-pc-linux-gnu-600a7a2b93bc09d0" ))
 ( .... )
 (dirN . '(normal-top-level-add-to-load-path 
"eln-x86_64-pc-linux-gnu-600a7a2b93bc09d0" )))

Maybe I missunderstand how this set of subdirs is ment to be specified,
but maybe some similar mechanism is possible?