ermmm… lots of places. :) It will vary a lot by local and subject areas but for starters. As a starting point, look up:
Universities. They often have all sorts of public lecture programs, for their students/academics and for the general public.
Some embassies arrange or host lectures on topics they care about.
Some of the smaller, top-level government bodies like the small business authority, technology agency, "entrepreneurship and innovation”… A local example of the last one locally: https://www.enterprise-ireland.com/en/Events/
Industry or professional associations (chambers of commerce, unions..) do some things.
You might find churches, religious community centres (google JCC in the US) that have relevant events
In smaller communities (where the above doesn’t exist), local schools might host these kinds of events for the general public.
I'm from Italy, and there tend to be small, single-day conferences around the country; you can find info on lanyrd, linkedin, facebook.. I can't tell.