VP9/WebM should work fine for Android. What's your code look like, out of curiosity?
There might be a better way of doing it, but I just have Ren'py read it as an image/scene. Might be worth a look. Like so:
Code:
image your_name = Movie(play="images/ani/your_ani.webm", loop=True, start_image="images/ani/yourani_060.png", image="images/ani/yourani_119")
image your_name2 = Movie(play="images/ani/your_ani2.webm", loop=True, start_image="images/ani/yourani2_060.png", image="images/ani/yourani2_119")
image your_name3 = Movie(play="images/ani/your_ani3.webm", loop=True, start_image="images/ani/yourani3_060.png", image="images/ani/yourani3_119")
Change the directory as per your own setup. 'start_image' should be the first image of your animation, and the latter should be final. This basically gets rid of the empty/checkered background look. Or should, at least. Then just reference it in your script (you should probably keep the above code at the top of the script for organizational purposes.) when it happens in your game. Something like this (code is from my own game. Ignore the 'relbasement46'. Likely not relevant to your case.):
Code:
mc "Fine, but you need to tell Eden first."
lil "She already knows. This was why we asked you to come over."
mc "Wait, what do you mean she already knows?"
lil "She wants to watch me have my way with you, she just won't know that you know about it. So, how about you stop crying and wrap your lips around this thing already."
scene relbasement46 with dissolve
lil "What a fit. Think you can swallow it all?"
lil "You can start sucking any day now."
window hide
scene your_name with dissolve
pause
window show
lil "I'd ask you how it feels, but obviously your mouth is occupied."
mc "Mmph."
lil "I don't like your tone, [mc]. How 'bout you do what you're told like a good girl and take this thing a bit deeper?"
window hide
scene your_name2 with dissolve
pause
window show
lil "Halfway there."
lil "I wonder if you can get all of it down on your own, though?"
window hide
scene your_name3 with dissolve
pause
window show
The 'scene your_name' should match what you have listed at the top. So, if the file's name is mc_bj at the top (image mc_bj = Movie(play=". . ."). . .etc.)
You call it later, like in the example above. So, basically: scene mc_bj with dissolve.
Might work for you. Worth a shot, at least. Hope you get it working regardless.