I never had a real reason to look at other distros with Gnome shell before. Earlier Ubuntu had a DE no one had.
Anyway, checking standalone apps, such as Chromium, that I took out of the Chromium snap in Fedora 31 beta. I just copied the whole folder
chromium-browser there and ran,
$ time ~/chromium-browser/chrome
In Ubuntu it was,
Just took the folder and put in Fedora 31 Beta. That folder is ~1/3 of the size of the Chromium snap in terms of MBs (607.3 MB snap, to 237.2 MB) . Just as portable!
Fedora installs Chromium browser normally, and the strange thing is it started slower than the one I took there.
$ time chromium-browser
Note: Of course, I can take the whole folder /usr/lib64/chromium-browser and place it anywhere and click on the executive file, and Chromium would start, also placed in Ubuntu. That one is also quite portable.