[the_third_wave]

It is a full port of VLC so it should be able to handle this task. You're probably referring to the frontend which differs from the ones used on desktop but that does not mean the functionality is not available. It is, you just access it differently. Either enable the 'Take a screenshot' option (Controls Settings -> Take a screenshot) and use that or send an intent to do so. The former works while watching videos, the latter makes it possible to automate this task from within termux, Tasker or Automagic.

You can also just install vlc in termux and use the command line interface:

   ~ $ apt search vlc
   Sorting... Done
   Full Text Search... Done
   vlc/stable 3.0.18-7 aarch64
     A popular libre and open source media player and multimedia engine

   vlc-qt/x11 3.0.18-7 aarch64
     A popular libre and open source media player and multimedia engine

   vlc-qt-static/x11 3.0.18-7 aarch64
     Static libraries for vlc-qt

   vlc-static/stable 3.0.18-7 aarch64
     Static libraries for vlc