Truffle Hunting in Croatia.....

I was so intrigued by your query that I looked it up on google.

https://unforgettablecroatia.co.uk/food-wine/truffle-hunting-in-istria/

It seems that the season is Autumn - September to December.

A great place to do that is near Motovun, Istria region. That is a lovely hill town (in fact, the most Italian hill town I’ve ever seen, although not in Italy). There’s a good truffle forest nearby. But I think my forum colleagues are correct that the season is fall, not spring. I did it while on a tour in September. Off season (for truffles) it will still be a lovely town and the shops will have plenty of truffle delicacies to sell you, but hunting them probably not productive.

My son went to this place and loved it!
https://zigantetartufi.com/pages/truffle-hunting

David - check out https://miro-tartufi.com/en/truffle-hunting/. We recently spent half a day with them in Motovun and can’t recommend more highly. Within 5 minutes of walking in woods his dogs started digging and within 20 minutes had found half dozen ping pong ball sized truffles. Back to his farmhouse for a spread of truffle snacks followed by truffled scrambled eggs topped with the freshly cleaned truffles we had just found. Dirt-to-table in under 2 hours! Lovely people and amazing setting at the foot of the walled city of Motovun.

We just went last week with Miro Tartufi https://miro-tartufi.com/en/ out of Motovun. I can't say enough good things about the experience. We were greeted with homemade schnapps at 10:00 am (when in Motovun...) and then went on an invigorating walk through the woods with Miro and his dogs. Watching the dogs work was fascinating. We found quite a few white and black truffles! Afterwords his wife Mirjana prepared us an incredible lunch with truffles made many ways, wine and even a truffle and chocolate dessert. We were the only ones who signed up that day so essentially got a private trip but it would have been equally fun to share it with others. 5 stars- highly recommended! Just check in with them to make sure it is a good time of year to look for truffles. I think they shut down in January. They also rent several properties both in Motovun and a cute little cottage on their hazelnut/oak planation. (Planted because they are good tree hosts for truffles).