It's not for everything (it doesn't even have the symbol in the article), but https://detexify.kirelabs.org/classify.html https://detexify.kirelabs.org/classify

It's not for everything (it doesn't even have the symbol in the article), but https://detexify.kirelabs.org/classify.html https://detexify.kirelabs.org/classify.html is useful for a lot of math stuff