Currently using BIv4 and Geniusvision. I am testing to replace Geniusvision due to lack of active development, specifically H.265 support. I (mostly) follow best practices and have a dedicated PC for NVR. I run Win10Pro to use the group policies to dictate how the OS runs so my system runs predictable and stable. My need to investigate a current alternative is because I updated the firmware on my cameras and now the H.264 bitrate is uncontrollable/unpredictable. H.265 runs flawless.
My reasons for not liking the following programs run from usability issues to a hot mess of a user interface, some I tested for a time, others were immediately uninstalled because they just sucked, some is where the documentation was unclear on what they provided or that they only worked with a certain brand of camera, some because of the license pricing: Viewcommander, Oodlecam, Anycam, iSpy, Xeoma, NetCamStudio, NetcamViewer, Camviewer, RK VMS, CamNebula, Geovision VMS,
Uniview EZStation, Polyvision, Freedom VMS, DSS Express, SmartPSS, Tinycam Monitor, ATVision.
The link fenderman provided above has even more programs I didn't find in my initial searches I started on last year, and may contain something better than what I've already tried.
Contenders I tested that moved closer to meeting my needs: Visec, Milesight, BIv5, Valerus, Milestone, iVideon, March Networks.
I very much liked DW Spectrum (NX Witness). It is an excellent piece of software and did everything I wanted it to do. It's expensive, and I was easily ready to drop the cash for 10-12 licenses, but it was taken out of the test pool because I have sent 2 emails to support with pre-sales questions (sent both pre and post COVID) and never received a response. There is no way I'm going to drop that kind of money when I can't even get a response to an email, because if that's the level of service before a sale, what about when I have a problem and I really need help. I think their licensing terms are quite restrictive for the money also. The strongest contender for a replacement I've tried is Luxriot, with a few caveats I think I can live with. I'm still testing for stability and have not committed yet. This is in addition to
Blue Iris. There are some things I like that Blue Iris does well, and some things I would like it to do that I just use a second program for. Blue Iris is used for streaming and scrubbing thru MD video, secondary program records 24/7 main streams. That's what works for me.
Your price point is going to be a strong driver in what you want to look at, ranging from free (but less features and support) to $70 and up PER CAMERA for a license, but with more expectation of more features and the support to match that price point.
That's why Blue Iris is so popular, it is the sweet spot, which is why since you already have this, it may be more beneficial to find out what the issue really is, unless you really want to try something new. I don't know what your budget is for a replacement.