I happened to notice that Reddit (and other companies) use
Atlassian Statuspage. He presents a free plan, which may serve the purpose. I'll have to look into it further.
I think this should work just fine for TalkImg website.
If this is not a secret, can you tell us how many visits you have in average now per day, week and month?
I use
BetterStack, which is free (up to a limit, more than enough for me) and very easy to set up.
From what I see on their pricing page, only differences compared to paid plans is more checks, more monitors, better support, etc. and that is not very important for Ninjastic or TalkImg website.
I think it's great they are proving free e-mail alerts, and 3 minute checks are more than enough.
I am sure this could easily be connected later with telegram and other platforms with notifications.