Welcome to the forum!
I think I find myself in agreement with Adubs here. The core ultra 7 265k is kinda expensive for your workload. I’d definitely split the builds. HomeAssistant can run on an odroid n2+ (in fact that’s used in their own home assistant blue variant, which was discontinued in favor of yellow, a rpi cm4 variant, but I digress). Also, the 265k has a massive power consumption compared to the 6500. Even if the 265k will be idling, it’ll likely use about as much power as the 6500 now.
I never ran frigate. But looking at it, the system requirements are minimal (intel n100). That’s where the might all-purpose odroid h4+ or h4 ultra comes into play. You can get either an intel n97 (which is actually newer and better than the n100 - thanks intel for your stupid naming convention) or the i3 n305 (basically an 8 core variant of the n97). I believe this should be capable enough for homeassistant and frigate.
Keep the old i5 6500 around, but remove the GPU and use the iGPU for jellyfin. I feel like most of your power draw is from the dGPU and if you can use the igpu for the encoding, you should be in a better spot. Or you could just buy 2x odroid h4+ boxes and have a theoretical total power draw of maybe 30W (excluding the storage).
Immich should be peanuts basically. Given the ultra 7 265k’s $400 price tag (just for the CPU) you can easily buy 2x odroid h4+ that will use less power for the job. Now the question then becomes: “do you have a switch already?” If you do, then perfect. If not, you’d probably still end up cheaper with 2 builds instead of one larger one.
For the lower power draw and for the price of the h4+, I find it hard to justify even going to a lower ultra 5 245k. The only disadvantage of the odroids is the lack of pci-e expansion. If you want to add stuff later, like a gpu, well… tough luck, because the thing only has an m.2 slot. But if you plan accordingly, you should be fine.
Bonus for split builds: you can keep the frigate + homass build 24/7 on, but be able to shutdown your jellyfin system to save some power while it’s not in use. You can then use the homass system to WoL the jellyfin system (assuming you don’t mind waiting maybe about 2 minutes for it to come online to save some power). But given that you’re running more than just jellyfin (you mentioned immich and minecraft), you’d probably be keeping the system online (which is still fine, the power draw is just so low).
The n97 is about 10-15% faster than the i5 6500, while using 1/4 of the power. I would’ve recommended the h4 ultra more, because the n305 is basically double the performance, but idk if you can use the igpu of the n305 for both frigate and jellyfin at the same time. And you said you have “a couple of users,” which means the GPU might’ve been a bottleneck (if you only have one for all your workloads). So in this case, 2x h4+ make more sense than 1x h4 ultra.
I still have to highlight that it really depends what you’re planning on doing in the future too. You could technically get something like the ultra 5 245k and add an intel arc a310 to power both your jellyfin and frigate systems (well, in theory you could jerry-rig an a310 on the h4 ultra, but that’d be too jank even for my standards - unless you get the h4 itx case and slap the adapter inside, somehow, without shorting something on the back, which should be doable and less jank).
But if you want to run more stuff in the future, then you might want to get a proper “full desktop” build (245k / 265k / ryzen 9600x etc.).
So it’s your turn to pick your poison. I personally really wish we’d see desktop systems that use less power.