I’ve spent a lot of time on the road, and it’s certainly possible to get a good workout in on a hotel bike.
The important thing is that the bike has some measure of power output - it doesn’t matter if it’s accurate, or even what units it’s in, as long as it is consistent.
Take the first 5-10 minutes to “calibrate” the power measurement on the bike using RPE for the kind of workout you are targeting - eg VO2max, sweet spot or endurance ride - and then use the power measurement on the bike to ride in the zone you are targeting. It’s possible to do both steady state and interval workouts this way.
If you ride on the same bike for multiple days, then it becomes easier to tweak things from one session to the next.