2020 iMac 27inch Supported Disk Drives

In short no. The reason being is in 2020 all the 27" iMacs came with SSDs and there is no place to install an internal hard disk AND there is no way to connect it to the computer. If you need additional storage for a 2020 27" your best bet is to either get an external SSD (what I'd recommend) or an external USB C external HD. What I'd recommend is one of the following:

https://eshop.macsales.com/item/OWC/S3D7E6GD10/ and to connect it to a 2020 iMac using the following adapter:

https://www.amazon.com/Cable-Matters-Adapter-USB-C-Inches/dp/B00ZPKNQYW/ref=sr_1_3?crid=188DW0QQF3SZ5&keywords=thunderbolt+4+ssd+adapter&qid=1657675262&sprefix=thunderbolt+4+ssd+adpater%2Caps%2C151&sr=8-3

The SSD I suggested is a 1TB model, however you can get them up to 4TB if you want. This is a simple and elegant solution.

Your welcome.