What MacOS is compatible with MacBook Pro Retina 15-inch Late 2013
What is the latest compatible MacOS for my acBook Pro Retina 15-inch Late 2013
MacBook Pro 15″, macOS 10.14
It is macOS Big Sur which you can obtain from How to download macOS - Apple Support
Note well that none of your 32-bit applications are supported on Catalina or later and that includes Adobe CS?, MS Office 2011, Apple's iWork '09 suite, etc. Use the free Go64 application to get a list of your 32-bit applications.
Remove any applications per vendor instructions that have installed device drivers in Mojave. These won't be supported in Big Sur and since Big Sur is on a read-only partition, you won't be able to remove the drivers afterward from System locations. Completely remove all useless anti-virus, so-called Mac cleaning software, and other third-party Mac "management" software.
Check with your printer/scanner vendors for driver support on macOS 11 and if not available, upgrading may not be right for you. Verify that your third-party vendors for existing 64-bit applications have continued to provide support for those applications on Big Sur.
Perform a last Time Machine backup of your current operating system, and then set that drive aside to not be used with Big Sur. Use a new, appropriately sized (2.5 - 3x your internal start drive) Time Machine drive formatted as Apple APFS once you have upgraded to Big Sur and all security/browser updates are applied.
