You might have a look at Librecast [0] which is a R&D project funded by Horizons Europe NGI0 programme via NLnet, aiming to the bring multicast to the current unicast internet and smoothen the transition of projects that adopt it. A great intro to multicast and Librecast is given in Brett Sheffield's 2020 LinuxConfAU talk "Privacy and Decentralization with Multicast" that is available on Peertube [1].

> To enable multicast on the unicast Internet we start by building an encrypted overlay network using point-to-point links between participating nodes. Once established, our overlay network can run whatever protocols we require, unimpeded by routers and middleboxes and which is resistant to interception, interference and netblocks.

[0] https://www.librecast.net/librecast-strategy-2025.html

[1] https://spectra.video/w/9cBGzMceGAjVfw4eFV78D2