Nativefier takes a URL and wraps it with the Electron framework, which runs the open source Chromium browser as its backend but runs as its own executable application. Nativefier is licensed under the MIT license and is available for Linux, Windows, and macOS.
Nativefier runs Chromium underneath. So it's able to remember your session just like any browser does. And it's worth reiterating that this is likely not going to be lighter on resources at all, but it may be a nice option for some who like to autostart specific web apps.
See Turn any website into a Linux desktop app with open source tools
Mastodon is a great open source, decentralised social network. I use Mastodon every day, and it's probably most common to use Mastodon through its web interface (although being open source, there are many different ways to interact with it, including terminal-based applications and mobile apps), but I prefer dedicated application windows.