Just found this thread after I fixed my elasticsearch container.
I didn't know about the TAKE_FILE_OWNERSHIP Variable, will have to check this later.
I just went to the /mnt/user/appdata/ folder,
chown -R nobody:users elasticsearch/
because it was root:root and
chmod 777- R elasticsearch/
(i know bad, will be fixed later).
Variable ELASTIC_PASSWORD didn't work for me.
Had to access the console of that container and
cd /usr/share/elasticsearch/bin
./elasticsearch-reset-password -u elastic
gave me a new password.
Then I was able to configure my Zenarmor OPNsense Plugin, httpS:xxx.xxx.xxx.xxx:9200 worked then as expected.