Like many others I have a lot of content on itch.io amassed through some impressive bundles they've had in recent years. I'm looking for an easy way to browse and launch my itch.io games and it got me wondering why Heroic doesn't have itch.io implemented by default. It would seem an obvious choice.
Not exactly what you are looking for, but lutris does support itch.io.
The way it is implemented, it won't list the bundle contents, but only games that have been added to your collection from the bundles, to avoid cluttering your interface / hide other games you purchased.
Yeah, I guess whichever launcher makes the most sense really depends on which storefront you tend to use most.
I mostly use gog, itch and humble bundle, which lutris handles nicely.
On the other hand, it isn't as streamlined as heroic for other stores, you need to install the egs launcher for lutris to run games from that platform, as an example.
Although it doesn't get many updates anymore, feels like it's on maintenance mode. It supports installing both Linux and Windows versions of games and even launching the Windows version with Wine, although without any DXVK/VKD3D options, it's kinda bare-bones, but for the generally simple indie games on the platform it usually works fine.