You can display memory information in
realme UI 7.0: Settings > Home screen & Lock screen > Home screen settings > Manage apps > Turn on Display RAM/Memory information for recent tasks.
realme UI 6.0 & 5.0 & 4.0 & 3.0: Settings > Home screen & Lock screen > Recent tasks manager > Turn on Display RAM/Memory information for recent tasks.
realme UI 1.0 & 2.0: Settings > Additional settings > Recent tasks manager > Turn on Display RAM / Memory information for recent tasks.
realme UI R Edition: Support it by default
realme UI Go & T & S & U Edition: Not supported