First determine the mount unit name with:

systemctl list-units --type=mount

It will likely be named after the mountpoint in /mnt such as

mnt-syncthing\x2ddeb.mount

for a mount point of /mnt/syncthing .

Then add this mount unit to the After= directive in your service, such as:

After=network.target mnt-syncthing\x2ddeb.mount

Now your service will wait for the mount before starting!

First determine the mount unit name with:

systemctl list-units --type=mount

It will likely be named after the mountpoint in /mnt such as

mnt-syncthing\x2ddeb.mount

for a mount point of /mnt/syncthing .

Then add this mount unit to the After= directive in your service, such as:

After=network.target mnt-syncthing\x2ddeb.mount

Edit your service with

systemctl edit --full [servicename.service]

to preserve the config after an update. Now your service will wait for the mount before starting!