Mikrotik Tutorial 30 Firewall Configuration - LAN and WiFi Client Isolation (2019) shows how to enable the use of the IP Firewall in the Bridge interface, then how to disable the default transfer in the Wireless interface and finally how to create a list addresses that can not communicate with each other and a filtering rule that performs this task.
For this tutorial, you will need one of the following Mikrotik routers:
Mikrotik RouterBoard RB951Ui-2nD hAP
Mikrotik RB3011UIAS-RM
Mikrotik Routerboard RB2011UiAS-2HnD-IN
Mikrotik RB750Gr2
Mikrotik hEX RB750Gr3
MikroTik RB2011iLS-IN
MikroTik Cloud Router CRS109-8G-1S-2HnD-IN
hAP lite
Hap
hAP ac lite tower
hAP ac
mAP lite
mAP
wAP RB951Ui-2HnD
RB951G-2HnD
RB2011UiAS-2HnD-IN
Mikrotik RB941-2nD-TC