I used to have 4k stuff, but my server is used by few family members and friends, and streaming 4k was just taking up to much resources. Upgrading to a more powerful NAS is planed when money is availible.

Also 4k uses conisderable more disk space and while I have 4k screen, I find 1080p with a good bitrate more than sufficiant for me. That saves a ton of storage.