The Galaxy S20 was launched in 2020, February 2020, even though this is a new device, I do not recommend buying a smartphone that was launched two years ago. While Samsung does offer up to 5 years of Android security updates, support for this model ends as early as March 2024. I recommend buying a smartphone that was launched in 2022. A very good list of Android Enterprise recommended devices can be found at the Android Enterprise Recommended Programme (which also shows when support for Android security updates ends).

https://androidenterprisepartners.withgoogle.com/device

The cheapest smartphone with 8GB RAM and 256 GB storage would be, for example, a Poco M4 Pro 4G, which is already available for 270 francs.