I can confirm @Kevinoid's suggestion works. What also works is prefixing "%h" instead of or replacing $HOME in the path of file/directory in systemd unit files.

see URL: https://bbs.archlinux.org/viewtopic.php?id=297777

"%h"equivalent to "$HOME", so can make work without /bin/bash -c 'exec part

Both work for me.

Cheers.