With Apple's iOS 14 update, and the changes it brings to data tracking, which will soon be rolled out, Snapchat introduced a new iOS 14 Resource Hub within its Business Help Center to guide Snap advertisers through the impacts the new changes should bring.
Explains Snap:

As you may have heard, Apple recently announced new privacy updates to the iOS 14 operating system. Apple's recent announcement indicates that these requirements will not be imposed until 'early spring', but we are here to help you understand and navigate these changes.

Apple's new opt-in process for ad tracking will mean that all the users accessing applications will be presented with a panel explaining what each application tracks and all the data it gathers.
Users will then be able to opt out of tracking if they so choose - which, given the nature of the prompts, and the broader rising concerns around personal data tracking analysts anticipate many people will do. Indeed, a recent report from MKM Partners suggested that Snapchat, along with Facebook, stands to suffer the most impact from the IDFA update.

It argues that Snapchat supports an increase in privacy and will comply with any requirements that iOS 14 imposes.
 
"Snapchat plans to show the tracking modal to users and continue to collect IDFA for Opt-in events on iOS 14. Snapchat will account for these changes with several recommended preparations around campaign management as well as new product capabilities."

Change of processes in its various guides and notes include that MMP user-level reporting is now being lost to those who opt out, and 28-day and hourly attribution windows are being removed.
Snapchat's full guides offer a host of answers on the most common questions while Snap's also running a webinar on the changes that are set to occur later this month:

Join us on March 11, 11am Pacific Time for a session called How to Prepare for Apple iOS 14 Changes: Web & App Advertising on Snapchat. You can register here. A recording of the session will be available on-demand as well."

Until these things play out, it is still impossible to predict what the complete impacts of the IDFA update will be and how that will shift approaches around ad. This guide, however, along with other published resources, will help advertisers prepare for the update and get a plan in place for any effects.