A networked media server doesn't need HDMI 2.1 and there are no 8K ripping devices or software. Fortunately, all the latest Nvidia RTX 3000 series cards are HDMI 2.1.
Unless you are planning on it being a HTPC inside the living room which is an entirely different configuration, a "server" can be any Windows 10 Pro PC with at least an i5 quad core or better with 16GB ram or better and any cheap graphics card an SSD drive for the boot and perhaps other SSD's or a beefy NAS if you plan to use Sonarr and Radarr for content retrieval. Any mid tower case is sufficient since servers can be stored anywhere in the house as long as you have an ethernet connection. My NAS is 67TB but you may be starting small with only a 4TB or 8TB hard drive inside the server case.
Ripping content can be done with MakeMKV and there's an endless supply of 4K and 1080p Bluray available online through torrents and usenet. Of course there is the ethical and legal questions here but the reality is, a lot people find it easier to download uncompressed movies in bulk rather than spend countless hours babysitting the ripping and organizing process of entering your own physical media.
A HTPC (Home Theater PC) will need more robust hardware and more expensive GPU with a pretty GUI and case with a wireless keyboard/mouse all in one type device or even a remote control.
PLEX Server is the ideal method of accessing your stored and organized content. With that on your server you can stream uncompressed movies and their audio to mostly any device with the PLEX app installed. Literally every modern TV and streamer has the PLEX app. I use Nvidia Shield Pro (3 of them) in my home to perfection.
I know this bit of info doesn't help you at all but this year I will have videos physically building a new media server to replace my existing one along with the software apps and configuration to automate populating the NAS with TV shows and movies along with configuring PLEX server. Start to finish turn key home media system that rivals kaleidescape but at a fraction of the cost. Essentially what you are looking for. There are videos scattered about Youtube covering pieces of the puzzle at different eras of home theater but nothing truly current, concise and all in one which I hope to change.
I have most of the parts sitting in my server room such as the ram, the 12 series i7 chip, PCiE4x NVME drives but got severely derailed on my
audiophile 2 channel stereo room project currently taking place. I'll revisit the media server build once i recoup my losses.