There are three places for HITMAN 3 players to check for scheduled server maintenance.
1. The latest patch notes
The HITMAN 3 patch notes give advanced notice of the incoming maintenance for that patch. Due to how the game is patched, it's not always possible for us to give an end time for the maintenance window. Each platform (PC, PS4, Xbox, etc) will be brought back online once all checks have been verified.
The Official HITMAN 3 Patch Notes page lists all of the patch notes: https://www.ioi.dk/patch-notes-hitman3/
2. IOI Twitter Account
Notice of any maintenance, as well as ongoing updates during a maintenance period, will be posted to the official IO Interactive Twitter account.
3. Hitmanstat.us website
The Hitmanstat.us website is not affiliated with IO Interactive but displays server information directly via an official API that we shared with our community. Read more about the website, and get a live service status overview, that includes maintenance, on the Live Service Status article.