you don't use yt-dlp ? 

 Normally, I do but I did everything from my phone, today.  

 There is a pretty good open source ffmpeg GUI app for Android too, can't remember the name but should be searchable

I forgot to mention picking the right output resolution is also important for fitting a 25MB limit 

 The resolution part, I got. I'll have to take a look for that ffmpeg app. I don't intend to make it a regular to edit on my phone 😂