I have a whole blog post talking about using Godot for GUI development. The short of it is that it’s surprisingly good but has a few drawbacks, and it doesn’t have a bustling ecosystem like webdev tools. I’ve yet to try it on mobile, though.

Video files are an exception since it would be too slow on WASM

Q: What happens with video files?

Video files get uploaded to our lightning-fast RTX 4000 Ada server. Your videos stay on there for an hour if you do not convert them. If you do convert the file, the video will stay on the server for an hour, or until it is downloaded. The file will then be deleted from our server.

VERT is really close but not totally what I was looking for, it’s a web app rather than a local program and AFAIK can’t convert videos locally, you’d have to upload it to a server and download them again.