Man, I'm so sorry to have f***ed up my post 2 times in a row.
all --include filters must not contain mcrypt:/h/.
So here's the logs:
rclone lsf -R "mcrypt:/h/" --include "a/*/" -vv --dump filters
--- start filters ---
--- File filter rules ---
- ^.*$
--- Directory filter rules ---
+ (^|/)a/[^/]*/$
- ^.*$
--- end filters ---
2021/11/29 02:02:46 DEBUG : rclone: Version "v1.57.0" starting with parameters ["D:\\Userdata\\bin\\rclone.exe" "lsf" "-R" "mcrypt:/h/" "--include" "a/*/" "-vv" "--dump" "filters"]
2021/11/29 02:02:46 DEBUG : Creating backend with remote "mcrypt:/h/"
2021/11/29 02:02:46 DEBUG : Using config file from "C:\\Users\\myname\\.config\\rclone\\rclone.conf"
2021/11/29 02:02:46 DEBUG : Creating backend with remote "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 02:02:47 DEBUG : fs cache: renaming cache item "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g" to be canonical "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
name "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 02:02:47 DEBUG : b: Excluded
2021/11/29 02:02:47 DEBUG : a: Excluded
2021/11/29 02:02:47 DEBUG : 4 go routines active
rclone lsf -R "mcrypt:/h/" --include "a/*" -vv --dump filters
--- start filters ---
--- File filter rules ---
+ (^|/)a/[^/]*$
- ^.*$
--- Directory filter rules ---
+ (^|/)a/$
- ^.*$
--- end filters ---
2021/11/29 20:10:06 DEBUG : rclone: Version "v1.57.0" starting with parameters ["D:\\Userdata\\bin\\rclone.exe" "lsf" "-R" "mcrypt:/h/" "--include" "a/*" "-vv" "--dump" "filters"]
2021/11/29 20:10:06 DEBUG : Creating backend with remote "mcrypt:/h/"
2021/11/29 20:10:06 DEBUG : Using config file from "C:\\Users\\myname\\.config\\rclone\\rclone.conf"
2021/11/29 20:10:06 DEBUG : Creating backend with remote "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 20:10:07 DEBUG : fs cache: renaming cache item "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g" to be canonical "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 20:10:07 DEBUG : fs cache: switching user supplied name "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g" for canonical name "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 20:10:07 DEBUG : b: Excluded
a/
2021/11/29 20:10:08 DEBUG : a/a1: Excluded
a/a.txt
2021/11/29 20:10:08 DEBUG : 4 go routines active
rclone lsf -R "mcrypt:/h/" --include "a/*/ " -vv --dump filters
--- start filters ---
--- File filter rules ---
+ (^|/)a/[^/]*/ $
- ^.*$
--- Directory filter rules ---
+ (^|/)a/[^/]*/$
+ (^|/)a/$
- ^.*$
--- end filters ---
2021/11/29 02:03:06 DEBUG : rclone: Version "v1.57.0" starting with parameters ["D:\\Userdata\\bin\\rclone.exe" "lsf" "-R" "mcrypt:/h/" "--include" "a/*/ " "-vv" "--dump" "filters"]
2021/11/29 02:03:06 DEBUG : Creating backend with remote "mcrypt:/h/"
2021/11/29 02:03:06 DEBUG : Using config file from "C:\\Users\\myname\\.config\\rclone\\rclone.conf"
2021/11/29 02:03:06 DEBUG : Creating backend with remote "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 02:03:07 DEBUG : fs cache: renaming cache item "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g" to be canonical "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 02:03:07 DEBUG : fs cache: switching user supplied name "mdrive:/kh/8ecjk22tnvfejgul0s1j4bfq7g" for canonical name "mdrive:kh/8ecjk22tnvfejgul0s1j4bfq7g"
2021/11/29 02:03:08 DEBUG : b: Excluded
2021/11/29 02:03:08 DEBUG : a/a.txt: Excluded
a/a1/
2021/11/29 02:03:08 DEBUG : a/a1/a1.txt: Excluded
2021/11/29 02:03:08 DEBUG : 4 go routines active
The log for the combination rclone lsf -R "mcrypt:/h/" --include "a/*/ " --include "a/*" -vv --dump filters was correct in my last post and indeed is the output I want. I don't understaand the workings though because as you wrote above the filters with single * are supposed to apply to files only and not folders.