Can I install the newest Apple system software on my iMac (Retina 5K, 27-inch, Late 2015)

Tips How to Upgrade to Big Sur 

There are several points to consider before attempting the upgrade to Big Sur. The most important is Due Diligence on the part of the User and is a Prerequisite for a smooth upgrade.  

The below points should all be consider Before attempting the upgrade.

Point # 1 - Are there pre-existing Unresolved Software Issues. They should be resolved prior to upgrading - they may carryover to Big Sur making the system unstable / unusable.

Point # 2 - Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. The Built-in Security of Big Sur is all that is required.

Point # 2 A - Commercial VPNs should only be used if Mandated by Corporate Head Office for working remotely. Otherwise - ones Privacy and Security touted by the VPN is suspect.

Point # 3 - What are the System Requirements ie: Empty Space Requirements specific to the Big Sur.

Point # 4 - Does the intended computer qualify for the upgrade.

Point # 5 - Are the installed Applications / Extensions compatible with Big Sur. Check with the Developer for compatible Apps / extension or do they offer updates. Same goes for Third Party Drivers for Printer, Scanners etc.

Point # 6 - If upgrading from Mojave and earlier versions of macOS - Remember that Big Sur does not support anything 32 bit. These include Applications, Extensions and Drivers for any devices. There is no workaround.

Point # 7 - Do I have a Rescue Plan In-Place. This comprises having 3 Backups using 2 methods and 1 Off Site incase of Theft, Loss or Natural Disasters. A Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS. For addition purposes - two Tested Bootable Clones each to separate external drives. This is insurance incase the upgrades goes sideways. At least one Tested Clone and / or Time Machine Backup should be Off - Site

Point # 8  - To upgrade to Big Sur will requires a quick, stable and reliable Internet Connection - preferred method is via Ethernet Connection. 

If not available and using Wifi - move computer as close to the Access Point / Router and disconnect all other devices connected to Wifi. Want the maximum bandwidth for the computer being upgraded to Big Sur.

What OS are you running, now? You can look in Apple menu > About this Mac.

If you are running High Sierra or earlier, you may have other software that will not run on Big Sur.

This program can help you identify which apps won’t run. https://www.stclairsoft.com/Go64/

You can then try to determine if there are updates or replacements.

Also, check with you Printer manufacturer’s website to make sure it will still work.

yes, big sur 11.4 is fully up to date. build 20F71

hi Barney-15E,

the OP stated in their question -- "And I currently am running macOS Big Sur Version 11.4 (20F71)."

Completely missed that. Has 11.5 been released?

not as of this afternoon. i looked at software update before replying. :)

Reported as RC 2 to Developers

P. Phillips wrote:

Reported as RC 2 to Developers

what does that mean in english?

Release Candidate formally Gold Master

thanks. :)

welcome :-))

…and I'm getting that my system is in need of an update.

I guess this is where I got confused? How are you getting that it needs an update? Is the Telehealth installer stating that?