Seriously, you have NOT done ANY Operating System updates in that time? You haven't updated any related drivers? Assuming you have, then realize your statement about not changing things isn't true - You are running patched/updated/changed code. And what about what you are running in the background?
And to make matters worse you are running a computationally demanding workload (OBS) in an emulation mode (and that emulation mode has had updates)
I accept changes must have occurred. For one, my setup doesn't work like it did, so something must have changed.
I haven't updated MacOS. I don't update unless something doesn't work, and even then, it's the last resort. I don't know if macs have drivers, but I haven't updated any. I've updated OBS, but my setup was working on the version I have. I don't know if/when/how Rosetta gets updated, if that happens automatically without updating MacOS. I'm using the exact same gear and haven't updated the firmware ( The Canon 90Ds have had no firmware updates, and I can't find any firmware update for my two Camlink 4ks, if there are ever any.) No update to the Caldigit TS3+ dock, but I tried bypassing it with no change. I'm not running anything in the background that I wasn't before, and I've tried closing every single thing running, and get the same result. I have a second M1 Mac Mini with almost nothing installed besides OBS (no plugins), and the same delay exists. I tried updating that Mac to the new OS, no change. And my brother, who has an iMac and a different-ish setup is experiencing the same delay I am, out of the blue.
I should mention that I used to stream using a 16 inch Macbook Pro 2019, and a iMac 2020 almost full spec, the iMac with added ram, and they both struggled with my stream. When I switched over to the M1 Mac Mini, the performance was outstanding. Temperatures stayed crazy low, fans were never heard even after streaming for over two hours, and life was beautiful. I was streaming like a dream, until one day, lag.
I'll add that, I've noticed a few of the podcasters I watch on YouTube streaming live have started to get delays as well, usually when they have a guest on, and I'm pretty sure those are the ones using Macs.
Again, I accept something must have changed. I've tried to figure out what. I've tried to remove/bypass everything I can think of. I tried another DSLR, another capture card, another Mac. I've tried older versions of OBS. I just don't get it. I'm open to suggestions.
I have not knowingly made any changes, but I do accept something has changed.