Not affliated but I stumbled upon this amazing lookup tool that can analyze devoiceable moras. https://devoice.siyuanyan.com
like how 助ける is た(す)ける with a silent u in su (in comparison with words like 滑る (すべる) where the す is not devoiced.
They don't seem to sell any services either.
Someone pointed to me their results seem to overlap with NHK's dictionary. Although I noticed they can also analyze arbitrary kana input.
by Madoshakalaka