From their announcement:

Important update: Amazon Luna on GOG
Hi everyone!
We wanted to give you an update about upcoming changes to Amazon Luna. As part of a broader shift in how Luna operates, support for external game libraries – including GOG – will be discontinued.
What this means in short: Luna will no longer offer access to GOG games via its cloud streaming service after June 10, 2026.
The important part: this does NOT affect your GOG library or ownership in any way. All the games you’ve purchased on GOG remain yours, fully accessible through GOG as always – just without the Luna streaming option.
For more details about these changes and what’s next for Luna, please refer to Amazon’s official communication.
Cheers!

Comments appear to be locked, so people are commenting on the first announcement about GOG and Luna:
https://www.gog.com/forum/general/bmore_ways_to_play_your_gog_games_were_teaming_up_with_luna_cloud_streaming_serviceb_b5660
Posting it here because, if I'm interpreting it right, the claimable games from (((previously Twitch Prime) previously Amazon Prime) previously Amazon Luna) Luna Premium will remain around for the foreseeable future. So, with claimable codes still around but not streaming, it sounds like a point for DRM-freedom, since people won't have the option that just normalizes stuff not being under one's own control.

This is definitely a sign that amazon gaming is healthy and not on the verge of shutting down

If this is going the way of Google Stadia, how's the controller itself?

Ironically, I've found the Google Stadia to have the best D-pad of any controller I've ever used hands down. Too bad its battery life sucks.

Idk I don't own it