The bitcoin satellite broadcast stuff uses a fork of the fibre codebase with changes to the FEC to better adapt it to recovering from signal disruptions. Otherwise it's not maintained anymore.

Fibre contained a number of complementary optimizations. A couple have been merged into popular node software-- that's what compact blocks (BIP152) is. The rest are still valuable particularly now with miners frequently including never-relayed transactions, CPUs having become ever more faster relative to latency, and some of the underlying number theory toys from proposed but not ever implemented further fibre enhancements having since been implemented for other purposes. Though the unmerged parts were the harder parts to upstream.

But with many of the contributors who worked on that sort of stuff driven out by vexatious litigation and other forms of harassment, I dunno if anyone will continue that work any time soon. Although, I think there has been some interest. The remaining contributors that I think are more likely to work on things like that have been busy developing an improved combinitoric optimizer for transaction selection, but that work is almost finished.

The two major things fibre had that are missing now is using a fountain code to fill in missing data from blocks and transmission over UDP. The two can be implemented independently but they're much more powerful together. Both are independently kind of complicated to implement in a non-yolo way: the error correcting code because it seems rocketsciency and so it narrows the pool of people willing to try working on it, and the UDP because it's a whole separate P2P protocol arguably, and has a lot of connection and resource management questions that have to be competently answered (some of which were just punted on in fibre).

Great answer @nullc, thank you for the context details. I always felt like having a subnetwork that was super fast optimized for sending transactions around the mempool would be really useful.

The optimizer is a fascinating knapsack problem to me. A lot of work in ETH land went on with this, especially with the work on Flashbots/MEV. But we hear less and less about it in the public these days.

Cheers