I see sites saying that Overcast has new widgets for the iOS 16 Lock Screen, but after having updated everything available, I still don’t see widgets. Oddly I also don’t see Carrot ones either. I’ve rebooted the iPhone 12 Pro Max and still nothing.
Check for updates through the App Store, and reboot your device once more after installing the update. The reboot to get widgets bug has been around since the iOS 15 betas unfortunately.
I don’t think the new version w Lock Screen widgets is out yet. The last OC update was 5 days ago, and Apple wouldn’t allow the iOS 16 apps in at that point. Wait for the update and you should be good - whenever it drops.
Change the language on your phone and then change it back to force an app cache reload. Overcast lock widgets are available on my phone. I had to do this trick to get Things, Fantastical, and Overcast widgets to appear.
As suggested by @Meatbag, changing the language apparently forces the widgets to appear. There is also a link somewhere about uninstalling the app and re-installing it.