Create the folder we will mount to

mkdir -p /mnt/myshare

Create a /etc/samba/credentials file with this format

username=myusername
password=mypassword
domain=mydomain // optional

Set the permissions for it to read only for root. chmod 400 /etc/samba/credentials

Create a /etc/systemd/system/mnt-myshare.mount. Setting vers=3.1 seems to be the latest supported by CIFS. uid=myuser,gid=myuser sets the read write permissions - in this case only myuser will be able to access to share. There is a requirement that the name of the share (in this case myshare) be the same as the folder mount point so a mnt-abc123.mount file would need to be mounted at /mnt/abc123.

[Unit]
Description=myshare
Requires=network-online.target
After=network-online.service

[Mount]
What=//192.168.1.100/myshare
Where=/mnt/myshare
Options=credentials=/etc/samba/credentials,vers=3.1,uid=myuser,gid=myuser
Type=cifs

[Install]
WantedBy=multi-user.target

Enable, start and check log

systemctl enable mnt-myshare.mount
systemctl start mnt-myshare.mount
journalctl -u mnt-myshare.mount

There can be a requirement to install smbutils for credentials file reading to work.