Welcome back to the Community Forms. Please remember that this forum is just that a place which is supported by both community and enterprise users in their own free time with the exception of the forum staff.
There also is not a need to keep bumping a topic if you are not getting a response (Re: ^^ We are volunteers and users of the community just like you). There are reports and filters that help topics that have gone unanswered to be more visible as well as an automated response after a few days if there have been no initial activity, by bumping your own thread these steps are not taken by the system.
For urgent matters as you are an Enterprise Customer, I would recommend that you open a support case through your Customer Portal (https://customerportal.uipath.com/) or directly through the Technical Support Form (Contact Technical Support).
With that out of the way, on to the original topic!
Deprecation is an indication that a version (typically a major version) will be removed in the future, and this is a way for the maintainers (UiPath) to inform users of such plans so that you can prepare for the eventual removal.
As defined by UiPath
Deprecation does not mean removal; it refers to functions or elements that are in the process of being replaced by superior alternatives. A deprecated feature means UiPath discourages its use but leaves it available. Deprecated features often face removal in future versions.
Generally speaking UiPath has been really good about informing users of features changes and deprecation of features over several releases. Usually a new feature will be introduced as experimental and opt in for users to try, in the next release or two they might make it standard and if it replaces existing functionality may mark the older functionality/way as depricated and usually a few more version after that the deprecated feature will be removed.
An example of this would be Modern Folders, originally called Organizational Units in 2019 Fast Track and prior, In 2019.10 Modern Folders was the opt in feature while Classic was the default and the functionalioty of the experimental Organization Units was rolled into Modern Folders. At this time not all functionality was supported in Modern folders such as Unattended Robots. By 2020.10 Modern Folders supported Unattended Robots and in 2021 Modern Folders is the default, while you can still enable Classic Folders it it recommended that you move away from them as they will be going away. (Some of those details might be off with the timing, but you get the idea)
The feature was depricated in 2021.4 and base on the following article it appears the NTLM authentication will be removed in 2021.10 and you should look at Authentication for external application using OAuth.
Hope that helps and gives you an indication of features / usage that you’ll want to look at before any planned upgrades.