could work as is.

configuration.ini.example

@@ -8,4 +8,5 @@ sshfolder=path to the .ssh folder to use
 remotehost=
 repository=
 passwordfile=
-dryrun=
+dryrun=
+

main.py

@@ -89,13 +89,18 @@ def restic_backup(dirpath: str, tagslist: list = None):
     if arguments.dryrun:
         dryrun = "--dry-run"
 
+    repo = arguments.remotehost
+    if repo.finds(":") != -1:
+        repo = f"{repo}//{arguments.repository}"
+    else
+        repo = f"{repo}:/{arguments.repository}"
     volumes = {dirpath: {'bind': dirpath, 'mode': 'ro'},
                arguments.sshfolder: {'bind': '/root/.ssh', 'mode': 'ro'},
                arguments.passwordfile: {'bind': "/repopassword", 'mode': 'ro'}}
     command = f"backup {dryrun} {tagscommand} {dirpath}"
     hostname = "restic"
     environment = ["RESTIC_PASSWORD_FILE=/repopassword",
-                   f"RESTIC_REPOSITORY={arguments.repository}"]
+                   f"RESTIC_REPOSITORY={repo}"]
 
     dockerhost.containers.run("restic/restic", command=command, environment=environment,
                               volumes=volumes, remove=True, hostname=hostname)