Man, I totally feel the frustration when gear just doesnt work right!! It is honestly the worst feeling when you are at an event and your flash starts acting up or just stops firing for no reason. I get so stressed out about reliability because missing a shot is just not an option!! If you are looking for a balance between price and not having your gear explode, here is what I think:

• Nikon SB-5000 AF Speedlight: This is the one if you want total peace of mind! It is fantastic because it has a built-in cooling system so it wont overheat. The price is pretty steep tho, which definitely hurts.
• Godox V860III-N Speedlight: I love this for a cost-conscious choice! It is amazing how much power you get for the price. The battery life is fantastic, but it definitely doesnt feel as indestructible as the Nikon. I always worry about third-party stuff failing, but that Godox is such a good deal compared to the OEM stuff!!

I am totally with Vintagevqm on the SB-5000 suggestion, especially if you can swing the price. That thing is a tank and wont let you down when things get heated at a long event. If you want something that feels almost as solid but for way less cash tho, I would suggest looking at the Godox V860III-N TTL Speedlight. I use it on my D850 and it has been surprisingly reliable for the price point so far. Just a heads up, be careful with the locking mechanisms on these third party units. They can feel a bit flimsy compared to the Nikon gear if you are swapping them out fast in the middle of a shoot. Quick tip for you: make sure you grab a few sets of Panasonic Eneloop Pro AA Rechargeable Batteries if you go with a flash that takes AAs. They have much better recycle times and wont leak like the cheap alkalines. I always keep an extra set in my pocket just in case. Youll definitely get the hang of it!

Godox V1 Pro is a good choice.

Honestly, I've tried a ton of different setups with my D850 over the years and it really boils down to how you actually work in the field. Before making a solid recommendation tho, I've got a couple questions to narrow it down. Are you planning to keep the flash on the hotshoe for those events most of the time, or are you looking to dive into a full off-camera setup for the portraits? Also, since you mentioned outdoors, are you trying to overpower the sun at midday or just looking for some subtle fill? That makes a massive difference in the power specs you'll actually need... the D850 is a beast but it needs the right pairing depending on the light you're fighting.