Went on some very tangential sentence mining binges during quarantine (mostly 2021) where I was picking up a crazy amount of Chinese. The single greatest source of these sentences is the example section from Baidu Fanyi (https://fanyi.baidu.com/) . When learning new words I would look them up on that website and it would give me a list of sentences using it (make sure you enable 传统机器翻译) which I would make cards from. It was either that or copy-and-pasted from chats with Chinese people online, or from random news articles, books, you get the idea. These are just a bunch of sentences that I hunted down myself and then accumulated over the years for the purpose of improving my Chinese.
Every card on here should have a natural-sounding Microsoft Azure voice, except for the early ones using Oddcast and the later ones being taken from actual Chinese-language movies and video clips. Some of the later cards (2022-23) also do away with the English translation and/or show the Hanzi only on the back (for the purposes of improving my pathetic listening skills). Some have images that are somewhat related to what is going on.