public class SubscriptionCharacterLocationConfiguration : IEntityTypeConfiguration<SubscriptionCharacterLocation>
        public void Configure(EntityTypeBuilder<SubscriptionCharacterLocation> builder)
            builder.HasKey(c => new { c.CharacterId, c.LocationId });
            builder.HasOne(c => c.Character)
               .WithMany(c => c.LocationSubscriptions)
               .HasForeignKey(pc => pc.CharacterId);
            builder.HasOne(c => c.Location)
               .WithMany(p => p.CharacterSubscriptions)
               .HasForeignKey(pc => pc.LocationId);
    [Table("Subscriptions_CharacterLocation")]
    public class SubscriptionCharacterLocation : EntityBase
        public int CharacterId { get; set; }
        public Character Character { get; set; }
        public Guid LocationId { get; set; }
        public Location Location { get; set; }
The issue
RowVersion is always being generated, no issues however with running the solution.
            migrationBuilder.AlterColumn<DateTime>(
                name: "RowVersion",
                table: "Subscriptions_CharacterLocation",
                rowVersion: true,
                nullable: true,
                oldClrType: typeof(DateTime),
                oldType: "timestamp(6)",
                oldNullable: true)
                .Annotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
Further technical details
MySQL version: new Version(10, 1, 31), ServerType.MariaDb

Operating system: Windows 10

Pomelo.EntityFrameworkCore.MySql version: 3.1.1

Microsoft.AspNetCore.App version: 3.1
Other details about my project setup:
          
Looks correct to me. You used the [Timestamp] attribute (which results in a rowversion) and you got a rowversion.

Depending on your scenario, you could also use the timestamp or timestamp(6) column type in combination with .ValueGeneratedOnAddOrUpdate() to generate something like this:
CREATE TABLE `SubscriptionCharacterLocation` (
  `RowVersion` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
What is it you would expect in your scenario and why do you think the current behavior is/could be a problem?
          
I have exactly the same problem.

Every time I add migration I get following code even if the model was not changed.
            migrationBuilder.AlterColumn<DateTime>(
                name: "Ts",
                table: "WaterMachines",
                rowVersion: true,
                nullable: true,
                oldClrType: typeof(DateTime),
                oldType: "timestamp(6)",
                oldNullable: true)
                .Annotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
            migrationBuilder.AlterColumn<DateTime>(
                name: "Ts",
                table: "WaterItems",
                rowVersion: true,
                nullable: true,
                oldClrType: typeof(DateTime),
                oldType: "timestamp(6)",
                oldNullable: true)
                .Annotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
            migrationBuilder.AlterColumn<DateTime>(
                name: "Ts",
                table: "Orders",
                rowVersion: true,
                nullable: true,
                oldClrType: typeof(DateTime),
                oldType: "timestamp(6)",
                oldNullable: true)
                .Annotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
          
Making the RowVersion property non-nullable, will workaround this issue:
// Using Data Annotations:
public class MyEntity
    [Required] // <-- Non-Nullable
    [Timestamp]
    public byte[] RowVersion { get; set; }
// Using FluentAPI:
public class MyEntity
    public byte[] RowVersion { get; set; }
public class MyContext : DbContext
    protected override void OnModelCreating(ModelBuilder modelBuilder)
        modelBuilder.Entity<MyEntity>(entity =>
            entity.Property("RowVersion")
                .IsRequired() // <-- Non-Nullable
                .IsConcurrencyToken()
                .ValueGeneratedOnAddOrUpdate();
        });
          
After updating EF Core and Pomelo MySQL to version 7, I would get an error on SaveChanges stating invalid SQL on RETURNING RowVersion, so I tried the mentioned workaround. I'm using MariaDB 10.3.
In my model I have the following, which worked fine with everything on version 6:
[Timestamp]
public byte[]? RowVersion { get; set; }
After changing it to the above workaround like so:
[Required]
[Timestamp]
public byte[] RowVersion { get; set; }
I'm getting the following error trying to apply the migration:
Failed executing DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
ALTER TABLE `R` MODIFY COLUMN `RowVersion` timestamp(6) NOT NULL DEFAULT '0001-01-01 00:00:00' ON UPDATE CURRENT_TIMESTAMP(6);