The UniFi Cloud Gateway UCG-Fibre has SFP+ ports that support 10 Gigabit connections. The USW-48-POE Switch has SFP ports that support 1 Gigabit connections as standard, and some models also have SFP+ ports for 10 Gigabit connections.

A direct connection from an SFP+ port (10 Gbit/s) of the UCG-Fibre to an SFP port (1 Gbit/s) of the USW-48-POE is not technically compatible, as SFP+ and SFP use different speeds and modules. For a connection via SFP/SFP+ ports, both devices must have either SFP+ ports or compatible modules with the same speed.

If the USW-48-POE only has SFP ports (1 Gbit/s), you cannot connect the SFP+ port of the UCG-Fibre directly to an SFP port of the switch. However, if the switch has SFP+ ports, these can be connected directly.

Summarised: SFP+ to SFP (10 Gbit/s to 1 Gbit/s) is not compatible. For a connection, both sides must have SFP+ ports or compatible modules with the same speed.

I doubt the automatically generated Galaxus response. The SFP+ ports of the UCG fibre support both 10G and 1G. Of course, a 1G SFP module must be used on both sides. A DAC cable will not work here.