How to handle server validation/errors?

Question

I'm dipping my toes into Blazor Server and I'm really unsure about how I should handle messages from the server back to the client in the event of an error or some server side validation. My brain instantly thinks "use a viewmodel", but is this the right answer?

I have this model:

public class Season
    {
        public int SeasonId { get; set; }
        [Required]
        public DateTime StartDate { get; set; } = DateTime.Today;
        [Required]
        [Display(Name = "Season Description")]
        public string SeasonDescription { get; set; } = string.Empty;
        [Required]
        public bool Publish { get; set; }
        [Timestamp]
        public byte[] RowVersion { get; set; }

        public virtual List<Game> Games { get; set; }
    }

I have a Season repository:

public interface ISeasonRepository
    {
        public Task<List<Season>> GetSeasons();
        public Task<Season> GetSeason(int SeasonId);
        public Task<Season> UpdateSeason(Season season);
        public Task<Season> AddSeason(Season season);
        // TODO: Implement Delete
    }

And, I have this service that is injected to my page:

public class SeasonsService
    {
        private readonly ISeasonRepository _seasonRepository;
        public SeasonsService(ISeasonRepository seasonRepository)
        {
            _seasonRepository = seasonRepository;
        }

        public async Task<List<Season>> GetSeasons()
        {
            return await _seasonRepository.GetSeasons();
        }

        public async Task<Season> GetSeasonById(int SeasonId)
        {
            return await _seasonRepository.GetSeason(SeasonId);
        }

        public async Task<Season> UpdateSeason(Season season)
        {
            return await _seasonRepository.UpdateSeason(season);
        }

        public async Task<Season> AddSeason(Season season)
        {
            return await _seasonRepository.AddSeason(season);
        }
    }

Previously using MVC, I would be creating a viewmodel and probably passing a message to it if we had any server logic that indicated if our model failed any server side validation/logic or if we had an error.

How is it best to handle this with Blazor? Should I still be using viewmodels? I've read about ErrorBoundary but it feels like they're for more critical problems that might cause SignalR state issue.

I can't get my head away from viewmodels but hardly any examples I read use such flow. How can I best notify my users the logic failed or there is something such as a SQL concurrency issue?