2020 Macbook Pro connected to new Samsung S8 won't allow a 60hz option

ah that appears to be a 4K resolution display with 10 Bits/color capability. "Frame Rate Max 60Hz"

Interfaces:

Display Port

1 EA

Display Port Version

1.2

HDCP Version (DP)

2.2

HDMI

1 EA

HDMI Version

2

When used with a USB-C cable, the maximum data rate attainable is limited to USB maximum speed of 20 GB/sec. the fastest DisplayPort data rate that fits inside that envelope is HBR2, with a maximum data rate of 17.28 G bits/ sec.

That data rate is nearly at the limit of the switching speeds and signal stability of the Electrical drivers used. Your USB-C cable should be a certified cable with a USB logo such as the USB 10 or 20 logo or better or the SuperSpeed Plus logo, and Must be no longer that ONE meter, unless a FAR more expensive ACTIVE cable is used.

Substituting a ThunderBolt cable can not improve the allowable speeds because this is a limitation of the USB drive electronics, generally not the cable itself.

A DIRECT HDMI will not improve speeds in this case, because neither the display nor YOUR Mac can run faster.

if you could find a TRUE ThunderBolt to DisplayPort adapter/cable, it could work slightly better, but most are only USB disguised as "Thunderbolt-port compatible" i.e., actually USB.

The specs I could easily found find indicated that S8 is an Android smartphone.

The Mac is not designed to give smartphones 60 Hz refresh rates. The data are updated only when changes occur, and not otherwise.