An internal development platform (IDP) put out by Spotify. Open source, but paid offerings.
When I was at Thrive Market, I considered both https://roadie.io and https://spotifyportal.com. We ultimately went with Spotify Portal, mainly b/c it had nicer visual polish. I later learned that it had less functionality than Roadie (but still enough that it was broadly useful). If I had to do it again, it would be just as hard of a choice b/c the visuals are the experience.
We didn’t have a ton of plugin usage. I authored one custom plugin to send data to DX. We heavily used TechDocs. A bit of time in Aika, but it was largely broken for us for most of the time I was there.