FFMPEG - Batch convert multiple audio formats in nested folders to AIFF & keep filename and meta data

I'm trying to convert all of my music library in various folders (mp3 / wav / m4a) to aif. I also need to:

1. Convert files in all nested subdirectories
2. Convert to 44khz 16 bit aif
3. Copy meta data to new file
4. Copy embedded artwork
5. Put all new files in the same output directory

I have spent some time going through answers on here but can only convert to aif so far;

find ./ -type f \( -name "*.wav" -o -name "*.aac" -o -name "*.m4a" -o -name "*.mp3" \) -exec ffmpeg -i '{}' '{}.aif' \;

Can someone help me update the script to do all of the things I need?

Any help mucho appreciated

(I've been through multiple posts explaining how to do each of these things but I can't get this to work on batch processing!)

I am unable to get [tag:ffmpeg] to add artwork to [tag:aif] file. Also, only Title and Comment fields are mapped/preserved (on my version). All others lost or not mapped.

Issue is with the [tag:aif] format as target output.

Feature/Bug reported.

Confirmed no problem adding artwork, mp3 -> mp3, and preserving all tags (except comment !!!).

My command:

ffmpeg \
-i "${fullpathfile}" \
-i "${startDIR}/${fileroot}.png" \
-map 0:a \
-map 1:0 \
-c:0 copy \
-c:1 copy \
-id3v2_version 4 \
"${libraryDIR}/${fileroot}.${sufOut}"

My environment:

Ubuntu MATE 20.04
Linux 5.4.0-135-generic 
#152-Ubuntu SMP Wed Nov 23 20:19:22 UTC 2022
ffmpeg version 4.2.7-0ubuntu0.1
libavutil      56. 31.100 / 56. 31.100
libavcodec     58. 54.100 / 58. 54.100
libavformat    58. 29.100 / 58. 29.100
libavdevice    58.  8.100 / 58.  8.100
libavfilter     7. 57.100 /  7. 57.100
libavresample   4.  0.  0 /  4.  0.  0
libswscale      5.  5.100 /  5.  5.100
libswresample   3.  5.100 /  3.  5.100
libpostproc    55.  5.100 / 55.  5.100

My test script:

#!/bin/bash
doTransform()
{    
cd "${libraryDIR}" ;
skip_start=0
time_end=unknown
while read line
do
#sufIn=mp3
sufIn=`echo "${line}" | awk '{ n=split( $0, val, "." ) ; print val[n] ; }' `
fileroot=`basename "${line}" ".${sufIn}" `
rm -f "${libraryDIR}/${fileroot}.${sufOut}"
ffprobe -hide_banner "${line}"
echo -e "\n sufIn = ${sufIn} ..."
echo " Hit return to continue ..." >&2
read k <&2 
case "${sufOut}" in
"${sufIn}" )
#codec="-codec copy" ;;
codec="-c:0 copy -c:1 copy" ;;
* )
case "${SufIn}" in
mp3 )	
#codec="-codec copy" ;;
codec="-c:0 copy -c:1 copy" ;;
* ) 	
# Issues with AIC/AIF format and codec specificaiton
codec="-c:0 copy -c:1 copy" ;;
esac
::
esac
#-to ${time_end} \
#-b:a 192k \
#-i "${fullpathfile}" \
ffmpeg \
-i "${line}" \
-i "${startDIR}/${fileroot}.png" \
-map 0:a \
-map 1:0 \
${codec} \
-ss ${skip_start} \
-id3v2_version 4 \
"${libraryDIR}/${fileroot}.${sufOut}"
###	MP3 -> MP3 :	metadata is preseved (except comment) for  
###	MP3 -> MP3 :	only Title and Comment preserved, all others lost
###  Try these again after upgrade to 22.04
#			-metadata title="Album cover" \
#			-metadata comment="Cover (front)" \
#			-metadata:s:a:0 title="Album cover" \
#			-metadata:s:a:0 comment="Cover (front)" \
done
}
startDIR=`pwd`
sourceDIR=${startDIR}/FFMPEG_Test
libraryDIR=${startDIR}/Output
sufOut=mp3
sufOut=aif
#-ipath "${libraryDIR}" \
#\( -ipath "${libraryDIR}" \) \
find "${sourceDIR}" \
-type f \( -name "*.wav" -o -name "*.aac" -o -name "*.m4a" -o -name "*.mp3" \) \
-print		|
grep -v '/Output' |
doTransform