You can download the videos without an extension like this:
- open the url of the video you want to download
- right click to open the context menu
- chose "inspect" and left click
- navigate into the search box and type "mp4" and hit "enter"
- a line inside the html-code will now be highlighted containing part of a link which looks like this ("
/file/934677102580717/")
- double click that line and copy that "link"
- now navigate to the address-bar and replace part of the current address ("
/watch/2021102019240282/?3") with the one you should still have in your clip-board.
- the address should now look like this "
/file/934677102580717/"
- hit enter
- the video will now play in your tab
- you can now right click on the video to open the context menu and select "save video as.." to save the video.