I had a jellyfin server on the same machine as my plex. I really tried to use both, the jellyfin experience was so much worse overall.
It had one technical feature that I valued (the ability to tone/color map dolby vision content for non dolby vision devices), but that was such a minimal feature for me (very little of my content is in the proprietary dolby vision colorspace).
I have a lifetime Plex Pass, but I'd gleefully dump it for open source if the experience were as good.
But as you say, it's not, and the lack of churn (only patch releases and one blog post this last 6 months) doesn't inspire me to think it's getting better nearly quick enough.
Are you talking about the Jellyfin server? It is quite an active project. Last release was 10.11.8 about a month ago, and github says that there have been 1049 commits to master since then.
It had one technical feature that I valued (the ability to tone/color map dolby vision content for non dolby vision devices), but that was such a minimal feature for me (very little of my content is in the proprietary dolby vision colorspace).