Since 5.3[1], we have automatic tests to decide if OpenCL is safe to use.

However, the user is not informed of if and why "Tools > Options > LibreOffice > OpenCL > Allow use of OpenCL" was turned off after turning it on and restarting - regardless of the reason (tests failed, not on device whitelist, OpenCL not installed...).
The only way to find out it was actually turned back off is to go back to the dialog.

We don't want to bother the user with too much information, but silently turning off what the user turned on is poor UX (and makes troubleshooting difficult).

We have reports about this issue:
- bug 103580 on macOS
- bug 106162 on Linux
- bug 133449 on Windows

And on ask.LO:
- https://ask.libreoffice.org/t/opencl-could-not-be-enabled/25011
- https://ask.libreoffice.org/t/unable-to-activate-opencl/45714

If the option remains exposed in the UI[2], the UX needs improving. Because OpenCL might be updated (or even just installed!) after LO was installed, I think it's OK to keep the workflow of automatically turning off after a check. However, we'd also need:
- so the user is aware that it did not work, a dialog at startup with the message:

"OpenCL was turned off because:
<reason XYZ>"

- In the Options dialog, a message like:

"Last attempt to use OpenCL failed: <reason XYZ>."

A link to a full log of failed tests would also be useful (similar to what we have for Skia since 7.6 for bug 155070). We have relevant user profile files opencl_profile.xml and opencl_devices.log[3], but I understand they are only available if OpenCL was able to be used.

Easy access to a short error message, + a full log with useful info, would be useful for the user to solve the issue themself (e.g. OpenCL not installed) or for QA to more efficiently troubleshoot.

[1]: https://meeksfamily.uk/~michael/blog/2017-02-01-under-the-hood-5-3.html
[2]: because of poor support on e.g. macOS, it has been suggested to remove the option from the GUI. See bug 103580 comment 12
[3]: see 8d3dd678bf9fd50a736cc0ff956f1efd7e660502 for bug 99453, and https://wiki.documentfoundation.org/QA/FirstSteps#Computation-related_issues_in_Calc_(_OpenCL_)