Ask HN: Where are the good search engines for mathematical formulas?

I am looking for effective search engines specifically designed for mathematical formulas. So far, my search has been disappointing; approach0.xyz is offline, onmath.com returns irrelevant results like p = m v when I search for F = m a, and search.mathweb.org appears to be a collection of abandoned projects. Does anyone know of a reliable tool for this purpose?

"in no particular order: https://matlas.ai https://www.mathdeck.org https://portal.mardi4nfdi.de/wiki/Portal https://www.theoremsearch.com/search https://ansumandas441.github.io/mathematical-discovery-engin..."