I have no idea if upgrading from 115 to 128 is broken like it is going from 127 to 128. Maybe follow the same steps as release to be safe idk.
The portable builds are fully portable, the profile directory is inside the browser folder. It does not touch appdata at all.
Notable bugs:
The 32 bit build is built with --disable-sandbox. With the sandbox enabled under Vista, the browser fails to open multiple processes which breaks the browser. The 64 bit build is fine. Considering Mypal68 globally disables the sandbox, I don't think it's that bad. If this really is a big issue then please pr a fix.
Changes on top of the previous 128.0.3-hotfix build:
All new r3dfox features from 129.x
Working menus in classic theme without zindex. Might be slightly faster.
Haven't tested on XP (OCAPI) nor have I extensively stability tested.
Please let me know what bugs or issues you encounter with it.