I got same issue, but resolved now after new update. It came out April 4th, 2019.
I can find the timer app now. I installed and works like before.
Back to liking the watch again.
Galaxy Wearable : 188.8.131.5231361
Gear S Plugin: 2.2.03.19032551
Do you have to have Sound mode on to get an audible alert/alarm with your timer now? I generally keep my watch in Vibrate only, but i would still get an audible alert with the old timer and alarm before the 2019 update. I stil do with the alarm, but the timer seems to only have an audible alert if Sound is turned on for the watch now. Am I missing a setting somewhere?