Unfortunately, official sites is dead-lock. I still use Mavericks among other options and love it, I also run Lion and have a boatload of apps that make me productive on both despite them being demoted as "old". I'm sure they'll be lots of things I don't know about or can't find, but I can probably help some people! So in the meantime, if there's anyone else still on Mavericks and you need compatible software for a specific purpose, please post about it here. I was originally going to write a very long post with all the great software and compatible versions I've found, and I may still do that at some point, but it's going to be REALLY long and I don't know when I'll get around to it. Modern macOS is no longer a platform I want to use, but I'd rather go back to an older version than outright switch to Windows or Linux. I've run into this a lot over the past few months because I'm trying to downgrade my life to Mavericks. I sometimes can't even find compatibility information listed anymore-the website will just say "Works on macOS™️!" with no mention of which Mac OS. Some time in the past couple years, this practice appears to have fallen out of fashion.
It used to be that when an app dropped support for an old operating system, they'd say something about it on their website, and include a download link for the last compatible version.