What is the broadcast address for the subnet 190.86.168.0/22?

190.86.168.255 is the broadcast address of the narrower /24 subnet 190.86.168.0/24; the /22 block spans four contiguous /24 networks and therefore has a higher broadcast address.

190.86.255.255 would be the broadcast address for a /16 block (190.86.0.0/16), which is a far larger address space than the /22 specified in the question.

A /22 prefix means 22 bits are used for the network, leaving 10 host bits (32 - 22 = 10): the lowest 2 bits of the third octet and all 8 bits of the fourth octet. Setting all host bits to 1 changes the third octet from 168 (10101000 in binary) to 171 (10101011 in binary) and the fourth octet to 255, giving a broadcast of 190.86.171.255 and a usable host range of 190.86.168.1 to 190.86.171.254.

190.86.169.255 is the broadcast address of the second /24 block (190.86.169.0/24) contained within the /22, not of the /22 supernet itself.