There is a new parameter in Set-SPOTenant in the SharePoint Online PowerShell Module in version 16.0.21513.12000, shipped Aug. 10, 2021 "StopNew2013Workflows". This will allow tenants to opt-in to disable the creation of new SharePoint Designer 2013 workflows, Existing 2013 workflows will continue to function and be editable. This was posted as MC279468 if you have the ability to look into the Message Center or know someone who can look for this message for you and email a copy.
Since these kinds of workflows can be used by many people, but not new tenants created after November 2020 (Support update for SharePoint 2010 workflows in Microsoft 365 - Microsoft Tech Community) I'm feeling like this a bit of a warning since its giving us (legacy users/admins of these workflows) the ability to turn the ability to create these workflows off. SharePoint Designer 2013 workflows are currently deprecated and *start conjecture* they are moving Designer 2013 workflows towards an end of life cycle similar to the way 2010 Designer workflows *end conjecture*. I haven't seen any published dates so, Don't Panic - but if you've been putting off planning to migrate your 2013 Designer workflows to Power Automate or another workflow software that has SharePoint Online integration... this may be a good time to start ramping up planning and getting those resources in place to handle that migration.