Hi @Nur Hossain,
Yes, there is a way to minimize downtime during patching in SharePoint 2019 with SQL Server Basic Always On cluster.
One approach is to use an approach called "rolling upgrade" or "rolling patching." In this approach, you patch one server at a time, starting with the secondary node, which can be removed from the SQL Server Basic Always On cluster, patched, and then added back to the cluster. Once the secondary node is patched and added back to the cluster, you can failover the cluster to make the secondary node the primary node, and then repeat the process for the previous primary node.
Please refer to MS document:
Best regards,
Seeya
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