Cegarth

It's a comedy spin-off web short series of My-Th that releases each week alongside the show, if you want to see segments of the riders just hanging around and being put into funny situations I'd recommend it, the comedy of these shorts are really great. This spin-off also has a few world building tidbits but nothing plot relevant as of when I'm writing this rec.

Both shows are done by the same main writer Naruhisa Arakawa. The show's red ranger personality and philosophical views are similar to Kuuga's protagonist Yuusuke Godai. In both shows most problems get resolved creatively rather than overly relying on the toys that the shows are promoting. At a certain point in Abaranger, a main villain who plays psychotic games against the heroes is introduced which has superficial similitudes to the Gurongi in Kuuga.

Kabuto's main writer Shoji Yonemura took heavy inspiration of Donbrothers' main writer Toshiki Inoue's writing style. Also Inoue is a frequent secondary writer in Kabuto. In terms of tone, atmosphere and plot progression, Kabuto is probably the closest tokusatsu to Donbrothers alongside Changéríon, despite having a darker setting.

The red ranger of Ressha Sentai ToQger has an appearance in Bakuage Sentai Boonboomger, so you might want to watch that season prior Boonboomger to appreciate his appearance more.