Finally I got it working.
Just follow Iridium's post in #5. But for step 4, you need to find the latest release on https://github.com/linuxserver/do…ompose/releases
For my RPi 3B+, I use https://github.com/linuxserver/do…r-compose-armhf. Then place this link back to the code in step 4 as
curl -L "https://github.com/linuxserver/do…r-compose-armhf" -o /storage/bin/docker-compose
and it works like a charm.