Honestly OP, TR is a power based training program. Obv the company doesn’t want to lose a segment of potential customers who have no power meter at all so they (and Zwift and others) have power estimator algorithms, but you really should at minimum have a power meter and preferably a smart trainer with power meter.
You can buy a non drive side pm for like $200-350 if you have a shimano drivetrain. You might want to consider that if you want to use a program like TR.