the command you would need to run Free Tube from a terminal would be freetube. out of curiosity, i installed it in a virtual machine and got about the same result as you are reporting. one video played, but stopped about 3/4 of the way through. the others just seemed to buffer and never played. in my trial, there was not terminal output to give any indication as to why the video wouldn’t play.
i don’t use any programs like that on my computer, but there are some threads here about youtube-dl if you want to search for those. i tried the suggestion (tartube) in this post. it also failed to download or show the video.
i know it isn’t exactly what you asked, but on my phone i use an app called newpipe which is installed through f-droid.