Since watchOS 26.0 my Ultra watch (1st gen.) has a battery drain issue. It can be fixed by a complete new set up which fixes the issue (battery lasts approximately 2 days) but the issue comes back after some weeks. Unfortunately the battery app does not show which apps are causing the battery drain (loss of 100% within 7 hours).
Apple Watch Ultra
To rule out a software issue inside your backup data, erase the watch and pair it again, setting it up as a new device. You will only lose your created Watch faces and may have to activate the cards in your Wallet app again.
Then test the battery life again.
Unpair and erase your Apple Watch - Apple Support
And also tell Apple Techs directly about your issue by using the Feedback link, so that they can fix this in an upcoming watchOS update.
Feedback - Apple Watch - Apple
The battery life on my Ultra 2 also got worse, 1.5% or more per hour, same usage pattern as before watchOS 26.
1 hour workouts, 530cal to close all rings.
watchOS 11.2 provided the best batter life for my watch, 1.1% per hour, and after 70 hours I had 18% left.
Most of the time my iPhone is with me, and the watch does not use the cellular network, only Wi-Fi and Bluetooth.
Apple Watch Ultra Battery Drain
