public class User
{
    public virtual Guid Id { get; set; }
    public virtual string FirstName { set; get; }
    public virtual string LastName { set; get; }
    public virtual Club Club { set; get; }
    public virtual Guid? ClubId { set; get; }
    public virtual UserProfile UserProfile { set; get; }
    public virtual Guid? UserProfileId { set; get; }
}

public class UserProfile
{
    public virtual Guid Id { get; set; }
    //.. other properties
}

public class Item
{
    public virtual Guid Id { get; set; }
    public virtual UserProfile Profile1 { set; get; }
    public virtual Guid ProfileId1 { set; get; }
    public virtual UserProfile Profile2 { set; get; }
    public virtual Guid ProfileId2 { set; get; }
    public virtual int Value { get; set; }
}

---------------------------------------------------------------------------------------------------------------------------
Id                                    | Value |  ProfileId1                      |        ProfileId2
---------------------------------------------------------------------------------------------------------------------------
8C8D6EBF-72BA-4AC9-93B1-0008232AD187    3       6593559E-A746-4441-458F-08D4D10C45C3    BEB4B0AF-2672-4F46-4558-08D4D10C45C3
3CE5E2A2-1CD1-41B1-BA68-001B3D790DFB    2       6BAD49F6-E66D-4DA7-4544-08D4D10C45C3    06582156-7615-4EED-4596-08D4D10C45C3
91FE73A8-E35C-4B75-BF15-00277C803B75    46      688033EA-8F25-4E14-454F-08D4D10C45C3    D588ED6B-6E03-4FFD-4541-08D4D10C45C3
907DBB00-AE3F-45CB-BF53-0039B5BCB0C9    10      76F56C17-9A67-48A6-455A-08D4D10C45C3    8447EDD8-4E4D-407A-456C-08D4D10C45C3
B66F8851-6150-4DE5-BCDC-008D4040AB24    38      4B6F9C8C-C9AC-40AB-4619-08D4D10C45C3    06932DB4-9065-45CE-4680-08D4D10C45C3
791CDD90-EAEB-4A2C-A5F9-0096AB9CB691    44      00A57E16-C629-46CB-4579-08D4D10C45C3    565129A2-66E7-4BBF-4569-08D4D10C45C3

var users = _dbContext.Users.ToList();
var clubUserData = _dbContext.Users
                .Where(x => x.UserProfile != null && x.ClubId == clubId)
                .Select(x => x.UserProfileId)
                .ToList();

var query = Items.Where(x => clubUserData.Contains(x.ProfileId1) || clubUserData.Contains(x.ProfileId2)).Select(p => new
{
    User1 = users.FirstOrDefault(u => u.UserProfileId == p.UserProfile1Id).FirstName,
    User2 = users.FirstOrDefault(u => u.UserProfileId == p.UserProfile2Id).FirstName,
    Value = p.Value.ToString()
}).ToList();