Terraform Plugin Framework : ListNestedAttribute Value Conversion Error

Terraform Providers
2

I have solved it by my selft.

schema changed to like this

			"subusers": schema.ListNestedAttribute{
				Computed: true,
				NestedObject: schema.NestedAttributeObject{
					Attributes: map[string]schema.Attribute{
						"username": schema.StringAttribute{
							Description: "The subuser username to be associate with the domain",
							Computed:    true,
						},
						"user_id": schema.Int64Attribute{
							Description: "The subuser id to be associate with the domain",
							Computed:    true,
						},
					},
				},
			},

and Create/Read section used like this

elements := []attr.Value{}
	for _, subuser := range domainsubuser.Subusers {
		elements = append(elements, types.ObjectValueMust(
			map[string]attr.Type{
				"username": types.StringType,
				"user_id":  types.Int64Type,
			},
			map[string]attr.Value{
				"username": types.StringValue(subuser.Username),
				"user_id":  types.Int64Value(subuser.UserID),
			},
		))
	}

	domainsubuserstate.Subusers = types.ListValueMust(
		types.ObjectType{
			AttrTypes: map[string]attr.Type{
				"username": types.StringType,
				"user_id":  types.Int64Type,
			},
		}, elements,
	)

A big thank you to @bendbennett you reference helped me to achieve this.