SQL Always on High Availabity Groups Multi Subnet

SQL 2017 Standard in SQL always on two node Basic AG. There are two DNS records for the listener with the different subnet IP's The servers are across subnets and we have hit issues with an application seeing to randomly time out when talking to the database, other times it responds in milliseconds. After running Wireshark we can see the application is trying to talk to the database via the failover partner listener IP address, the none readable replica. This information I have read explains the 21 second timeout. https://techcommunity.microsoft.com/t5/sql-server-support/improved-multisubnet-listener-behavior-with-newly-released-sql/ba-p/318664 MultiSubnetFailover=TRUE seemed like the resolution but the application is using an older version of .NET is there anything else I can do to resolve or work around this?