OpenCL is enabled by your GPU AMD Driver.
Download GPU-Z and see if your GPU card has OpenCL check marked. If it does then OpenCL is enabled and working.
If you installed the latest GPU AMD Driver and GPU-Z shows OpenCL disabled, no check mark on OpenCL Box, then your AMD installation was probably corrupted or you download the wrong GPU driver.
Here is the latest AMD Driver for the RX 580: https://www.amd.com/en/support/graphics/radeon-500-series/radeon-rx-500-series/radeon-rx-580
Try installing or removing the current AMD driver by using this basic method:
Uninstall the current AMD Driver using DDU as per this method:
It could be due to a corrupted AMD Driver installation.
Download free program DDU (Display Driver Uninstaller). Run it in Safe mode with the internet disconnected.
You can also run it in Windows Desktop but then you would need to Reboot the computer for DDU to finish erasing all of the AMD Driver traces from your computer.
Once it finishes uninstalling the current AMD Driver in Safe mode and boots back to Windows Desktop, still with the Internet disconnected, delete the AMD Installation folder C:\AMD if it was created before.
Now install the full AMD Drive package you downloaded manually from AMD Download page. Not the express package. Run the package and if it installs correctly again delete C:\AMD folder and reconnect the internet.
This should prevent any conflict when installing the new version from the previous version.
By the way, C:\AMD is always created whenever you run the AMD Driver package
Make sure your Dell PC has the latest BIOS and CHIPSET installed plus if you have a Intel APU make sure you have the latest Intel Integrated Graphics installed: Support for Inspiron 5675 | Drivers & Downloads | Dell US
The latest AMD Driver works correctly if the Intel Graphics is the latest and Windows is fully updated via Windows Update.