The first step is ensuring you are on compatibility level >=130. Run this query to find out the current compatibility level:

SELECT compatibility_level FROM sys.databases WHERE name = DB_NAME();

Check if In-Memory OLTP is supported for this server edition and database pricing tier. This has to be 1.

SELECT CAST(SERVERPROPERTY(N'IsXTPSupported') AS BIT) AS IsXTPSupported

Next, list tables where this is switched on:

SELECT SCHEMA_NAME(schema_id) SchemaName, name TableName
FROM sys.tables
WHERE is_memory_optimized = 1;

For any memory-optimised tables

-- EF Core 6
modelBuilder
    .Entity<Blog>()
    .IsMemoryOptimized();

-- EF Core 7
modelBuilder
    .Entity<Blog>()
    .ToTable(b => b.IsMemoryOptimized());

More info microsoft and red-gate and github