Add-ons grayed out

Hi. I’m using Seamonkey 2.49.3 on a Linux box, 64-bit. When I search for addons, I find the vast majority to be grayed out. I’m wondering why this is so. I’m looking to duplicate some of the helpful addons I use in Chromium, but I don’t see how to do it. Why are so many grayed out? Thanks.

SeaMonkey doesn’t support the new extensions format (WebExtensions), so the majority of newest versions won’t work for it. You might be able to find compatible versions if you look for older ones.