In my Samsung Galaxy S4 phone, most animations work very slowly, around 1 FPS or slower. There are intermittent delays between frames. Doing the same thing over and over usually makes the action smooth after a while. Here are some specific observations:

• In Gallery, the app bar enlarging/shrinking while scrolling at the top (this was always slow no matter how many times I tried, or maybe I didn't try enough number of times since it takes too long)
• In stocks app, scrolling enough so that new cells are populated (tiny-distance scrolls are usually smooth)
• Left menu appearing for the first couple of times in Stocks app (afterwards it's always smooth)
• First tab switch in stocks app (afterwards it's smooth)
• Going into a stock in stocks app (pressing back and going into the stock again is smooth)
• Optimistic/pessimistic switching in stocks app (after 4-5 switches it became smooth)

Also, when I check "Performance Overlay" in Gallery, nothing changes. I do not see that profiler kind of graph at all. Checkerboard Raster Cache Images works though.

These are the Gallery app that I run using flutter run --release and Gallery and Stocks apps that I downloaded from here: https://build.chromium.org/p/client.flutter/waterfall?show=Linux . Unfortunately I cannot test Flutter Gallery et al. in Play store since they are not available in my country.

Here are details about my phone:
Samsung Galaxy S4 (GT-I9500)
Android 5.0.1
Rom: Omega v28 - UBUHOE3

@eseidelGoogle said it may be a quirk related to this device's GPU. I'd be happy to run things and send back logs, or help in any other way.