This script simulates user activity, preventing automated suspension, if any file is begin accessed through samba server. Works on Plasma 5.

prevent_suspension_on_samba_activity.py

#!/bin/env python3

# This script simulates user activity, preventing automated suspension, if any file is begin accessed through samba server.
# works on Plasma 5, and, AFAIK, not Gnome
# based on https://bbs.archlinux.org/viewtopic.php?pid=1797228#p1797228
#
# Uses smbstatus (which requires root permissions) to find if samba is locking some file or directory.
# Do not run with sudo (wouldn't be able to connect to the SessionBus), instead
# add smbstatus to the sudoers file, to allow running it without password, for example:
# username ALL = (ALL) NOPASSWD: /usr/bin/smbstatus
#
# Put this script in $HOME/bin/ and add it to KDE's startup applications

import os
import subprocess
from dbus import SessionBus
import time
import sys

POLL_LOCKED_FILES_INTERVAL = 15 #minutes

def smb_locked():
    p = subprocess.run(["sudo", "smbstatus", "-nbL"], check=True, capture_output=True)
    out = p.stdout.decode("utf-8")
    smb_clients = filter(None,out.split("\n")[3:])
    return list(smb_clients)

def keep_active():
    print("keeping active")
    session = SessionBus()
    screensaver = session.get_object('org.freedesktop.ScreenSaver', '/org/freedesktop/ScreenSaver')
    screensaver.SimulateUserActivity()

def main():
    print("keep-active started")
    try:
        while True:
            if smb_locked():
                keep_active()
            time.sleep(60* POLL_LOCKED_FILES_INTERVAL)
    except KeyboardInterrupt:
        sys.exit()

if __name__ == "__main__":
    main()