About a month ago, when I asked in this forum which 3rd party adapter was good, someone answered that Fotodiox and Viltrox would be good. So I ordered it from China (actually 6 weeks ago) and I got it today finally.
At first, nice case
Nice package. It has a certificate and manual!
Nice looking.
It looks good although it is lighter and its finish definitely looks cheaper than the original Canon adapter.
AF works beautifully with all EF/EFS lenses that I have. Not a problem. No complaint.
HOWEVER, it was not long before I found a problem.
.
Look at the photos. All were taken with EF 50mm 1.4 at F/4.
Viltrox Adapter
Look at the strong flare!
First I took off UV filter, which is of B+W.

It was not a solution. Then, I made an additional hood at the right side of the lens with my hand and got the following. All photos here are taken with my 50mm attached with the original hood.
Viltrox Adapter + Hand
Then I switched the adapter back to the Canon original one.
Canon Original Adapter
The problem is gone basically although the image is not clear enough.
One more with a hand hood.
Original Adapter + Hand
Now better.
IMO, it is due to the inside material with a glossy finish. I do not understand that a photography company is making such a product. They seem to care about their package, but not about the quality.
.
Today I found the following reply:
https://www.dpreview.com/forums/post/61572754
I should have waited for this reply or read all replies carefully.
Do you have any idea how to paint the inside with a black unshiny paint?
Do not follow my step. No Viltrox adapter.