Newest first. Chrome and Brave zips are listed above the Firefox build of the same version.
The Chrome Web Store
and Firefox Add-ons
builds update themselves; these files can be newer because they skip store review.
The Firefox file is unsigned. On the regular Firefox, load it from about:debugging → This Firefox → Load Temporary Add-on. It is removed when you quit Firefox.
Keep the same folder when you update a manual Chrome or Brave install.