I use Pegasus at the moment as it's extremely customizable, although it does have a bit of a learning curve since you do most things through media.txt files. You can configure launch commands, box art/media/videos through an external scraper (I use Skyscraper), and you can point to bash files which opens up use of the terminal for basically anything you want to do OS side. It also has many different themes, basic metadata, and sorts games by system.
Emulation station is also another popular choice and is more out-of the-box minded bit still requires a bit of know how.
I also really like Playnite because it's video game sorting heaven, but sadly it's windows only and is really janky in wine/lutris. I eagerly await the day a working linux port arrives.