Install

sudo apt install -y s3fs

Create credentials

echo ${BUCKET}:${ACCESS_KEY}:${SECRET_KEY} >> ~/.passwd-s3fs
chmod 600 ~/.passwd-s3fs

Mount S3 bucket

s3fs bucket1 /tmp/mnt -o url=https://s3.example.com

Parameter

-o passwd_file=~/.passwd-s3fs
-o url=https://s3.example.com,allow_other,umask=0000
-o use_cache=/tmp/cache

/etc/fstab

mybucket1.mydomain.org /mnt/mybucket1 fuse.s3fs _netdev,allow_other,passwd_file=/home/ftpuser/.passwd-aws-s3fs,default_acl=public-read,uid=1001,gid=65534 0 0

Links
https://github.com/s3fs-fuse/s3fs-fuse
https://gridscale.io/community/tutorials/s3-fuse-ubuntu/