I'll see if newpipe will let me encode to webm. 👍🏾🔥
Discussion
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 😂