Can an iPad 2020 be connected to a USB-C monitor?

You are correct that the iOS devices using USB-C chips need no adapters for video out to most USB-C displays. The lightning based hardware require specific adapters like the HDMI or VGA ones Apple sells.

• Lightning Digital AV Adapter https://store.apple.com/xc/product/MD826AM/A
• Lightning to VGA Adapter https://store.apple.com/xc/product/MD825AM/A

I’ve never seen an adapter that fits your requirement. The above “adapters” have embedded systems on a chip “SoC CPU” that boot each time you connect them to convert video out data streams into the HDMI or VGA signals needed to drive displays.