Ah I see you mentioned the cuts are only a few seconds long. This wouldn’t catch that very well.

If you have a server outside of your network you could simply hold open a TCP connection and report when it breaks, but I’ll admit at that point it’s outside of what I’ve had to deal with.

Depends on how much you want to set up. For my purposes, I just check for connectivity every minute, and record true or false as a new row in a sqlite database if there is connectivity.

This is what I use on my raspberry pi,

#!/usr/bin/env python3
from datetime import datetime
import sqlite3
import socket
from pathlib import Path

try:
    host = socket.gethostbyname("one.one.one.one")
    s = socket.create_connection((host, 80), 2)
    s.close()
    connected = True
except:
    connected = False
timestamp = datetime.now().isoformat()

db_file = Path(__file__).resolve().parent / 'Database.sqlite3'
conn = sqlite3.connect(db_file)
curs = conn.cursor()
curs.execute('''CREATE TABLE IF NOT EXISTS checks (id INTEGER PRIMARY KEY AUTOINCREMENT, timestamp TEXT, connected INTEGER)>
curs.execute('''INSERT INTO checks (timestamp, connected) VALUES (?, ?);''', (timestamp, 1 if connected else 0))
conn.commit()
conn.close()

and I just have a crontab entry * * * * * ~/connectivity_check/check.py >/dev/null 2>&1 to run it every minute.

Then I just check for recent disconnects via:

$ sqlite3 ./connectivity_check/Database.sqlite3 'select count(*) from checks where connected = 0 order by timestamp desc;'

Obviously, it’s not as full-featured as something with configurable options or a web UI etc, but for my purposes, it does exactly what I need with absolutely zero overhead.