Nightly seems to work like a charm. Installed on my NVMe by flashing it. Came up, rebooted. Did some basic config (via keyboard / mouse / monitor), hooked it up to my TV and used the remote for the rest. Video and audio works (I'm using a soundbar). Decoding and transcoding works as well. Just had to get used to indexing of Kodi (it is more strict than Jellyfin), but I can deal with that.
Thanks for all the work to get this running on RK3588!