How to select the title frame (poster, cover) of a video clip when uploading to VKontakte, YouTube and similar services?

Question

YouTube

Sometimes you want to post some kind of video, but the “picture to attract attention” is far from being the most interesting frame from it. Is there a way to select it manually? Maybe video pre-processing (if so - preferably a recipe using a free tool like FFMPEG or VLC, but it will go to the extreme and proprietary) will help?
PS: Surprisingly, we don't have a video tag here!

Answer 1

On Youtube, you can upload any picture as a video cover. True, this feature becomes available when you are a YouTube partner and the channel has a good reputation

Answer 2

And I have another usecase. Recently, somehow it was required to upload to YouTube as much as a 20-minute video. After uploading the video, YouTube offered to verify my account in order for this video to be available. Verified via sms. After that, the ability to upload any JPEG as a freeze frame became available.

Answer 3

You need to verify the channel and have a good reputation. But if you load it from the screw into VK, then only the first frame gets on the cover