Big Sur running slow

Thank you for the Report ;-))

The biggest aspect to the slow performance is the Internal Rotational / Mechanical HD with the slow 5400 RPM speed.

No matter how clean the installation and other software installed by you - this drive is going to hold the performance back to what is being experienced.

The options to speed up the whole system could be to purchase as External SSD Drive large enough for your storage needs.

Then either Clone the existing Internal Drive to the External SSD and run the OS off the external Drive.

The existing Internal Drive could then become your Storage or possibly the CCC of the External Drive.

disk0 - APPLE HDD HTS541010A9E632 1.00 TB (Mechanical - 5400 RPM)

System modifications - There are a large number of system modifications running in the background.

Plugin: /Library/Internet Plug-Ins/Flip4Mac WMV Plugin.plugin installed 2008-08-15)

Plugin: /Library/Internet Plug-Ins/Silverlight.plugin

Suggest downloading the Application Etrecheck directly from a Well Respected ASC Contributor. The application is free or paid from added features. Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ). It will take a Snap Shot -  both the hardware and software. The Report will Not Reveal Any Personal Information. Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

Any Third Party Applications that will interfere with the normal operation of the OS, alter, modify, remove or delete or attempt to do so is an invitation for disaster and may require a Reinstallation of the OS.

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

Security updates disabled - Security updates are disabled. This computer is at risk of malware infection

Apple security disabled - Apple security software is disabled. This computer is at risk of malware infection.

The Larger number System Modifications are attributed to the Third Party Application installed that may not be totally compatible with the upgrade to Big Sur.

As well the Unsigned Applications - meaning the Software Certificated from the Vendor are not Recognized by Apple as Notarized by Apple. Anything under the Unsigned Files in the supplied Report falls into this category

Added are two out dated plug-ins

Plugin: /Library/Internet Plug-Ins/Flip4Mac WMV Plugin.plugin installed 2008-08-15)

Plugin: /Library/Internet Plug-Ins/Silverlight.plugin

What Mac OS version did you have before Big Sur?