Kepler-90 ( KOI-351 ) - Eight Planet, Compact Solar System Analogue

Analysis of the TTVs between planets g and h indicate that planet g has a very low density. Planet h appears to be relatively typical.

Liang et al. "Kepler-90: Giant transit-timing variations reveal a super-puff"
https://arxiv.org/abs/2011.08515

No evidence for rings at the sensitivity of the Kepler data (which isn't the same thing as ruling them out):

Quote :

An alternative explanation is that these planets have large optically-thick rings, which could give an appearance of a larger planet. We have searched for a signature of a tilted ring in the transit data (Heising et al. 2015), but found no evidence of it. This however does not mean that this explanation is ruled out, as the data do not have sufficient sensitivity to distinguish between most of the ring versus no-ring solutions.

No evidence for a massive exomoon or an unseen planet perturbing the system either.

Quote :

We thus conclude that the 2 planet solution we found is strongly favored and there is no need to add a third body, and there are no found solutions that do not involve the mutual perturbations between the two planets as the the main origin of observed TTVs.