I’ll echo @doobeh - above all else, figure out if you can bring a blower fan (or any kind of fan that you can position well) with you. Then use the outdoor version of the workouts that go by rate of perceived exertion.
In environments where you can’t control the cooling as much as you’d like, I’ve found (and I think @Nate_Pearson mentioned this on a podcast) that VO2max intervals with an equal ratio of work duration to rest duration (e.g., 2 minutes at RPE 9, then 2 minutes spinning easy) work well, because the longer work duration, the worse the heat builds. Going by RPE and using a very simple structure like that, all you really need is a stopwatch.
Over the course of two months you can mix in more progress by increasing the length of the individual intervals (starting at 1 minute, working up to 3-5 minutes) and slowly working up from 15 minutes total VO2max effort to 20 minutes. Maybe increase the total duration every week by 30-60 seconds, while increasing the length of individual intervals by 60 seconds every week (reducing the number of intervals as appropriate to hit the right total duration).
If you have the money, a pair of power pedals can go onto almost any indoor bike. Garmin’s Vector 3 pedals are the best for this, but the Favero Assioma pedals work on quite a few indoor bikes as well.