Foremost, trading with no volatility means that there is a lack of market participants and, in particular, liquidity providers.
The greatest risks are borne by traders with large deposits, who need sufficient liquidity in the market for closing their positions. Thus, there is a risk that large positions in low-liquid instruments can be closed with a large time lag, which usually leads to significant losses due to closing the position at very unfavorable prices.
Another risk is the long and narrow price range where your position will be stuck for a long time before going breakeven or profit.
The list of instruments sorted by volatility is changing rapidly due to migration of capitals shifting from one to another instrument.