If anyone has one, and carries it, I would like some advice on holsters.
What you settled on and why.
I am not a big guy, kind of skinny, thinking inside waistband. Since I am #6345 on the waiting list to pick it up I have some time to mull it over. 🙄

I'm on the skinny side too, it can make carrying a little challenging. I can't speak to the 365XL but I have been using Alien Gear IWB for a G19 and 43 and like it pretty well. I just ordered their Shape Shift Modular Holster System for my new 365 and an extra shell for my "about to purchase" G48. It will give me a couple options for carry depending on the situation. I am planning AIWB for the 365 and IWB at the 4 o'clock for the G48.

I carry my 365 XL daily IWB in a Milt Sparks VMII that I bought originally for a Kahr PM9 many years ago. Fits fine once it's in the holster. Just have to shove it in a little harder because of barrel length difference to make sure it stays in battery.

I'm sure Milt Sparks now makes one exclusively for the 365 XL now.

https://www.hawgholsters.com/store/p93/Sig_Sauer_IWB%2FAIWB_HAWG_Holster_with_Ulticlip.html

Some good suggestions here. I do have a Milt Sparks holster and they are very well built. The wait time is long though. The Kydex holsters that are “hybrid” seem to have the best of both worlds and are available.
Appreciate the reply’s, there is a lot choices. Probably to many.😁

Although I have not used a Summer Special since the 1990s, be aware that Milt Sparks usually keeps some in stock for the P365 XL. https://www.miltsparks.com/store.php#!/Summer-Special-2/c/28350085

Another thing to consider is whether you intend to put a red dot sight on the gun, because some may not work with the dot sight. I usually order a Sparks Criterion as soon as I decide to keep a gun, but I did not do it in the case of the P365 XL because it may need to be molded differently for a dot on the gun. I bought a much cheaper kydex holster that turns out to work fine with or without the dot sight. I don't really like the ride or cant on the holster, but it works for now while I decide whether I am going to keep the dot sight on the gun. (local dirt's holster looks like it may work either way, but the holster was not designed for that gun so it may look different if you order one for your gun.)

I've been using a PJ Holster kydex IWB for about a year now for both a 365 and 365 XL. I'm not skinny and got them due to the minimal width. I can wear them in my normal jeans without going up a size. They've both held up well and are easy to put on but stay put.

https://pjholster.com/

Lots of makers out there and I'm sure most of them make a good product but I can definitely recommend this one. Lead time is currently about two weeks if that's a factor.

I like PJ for all Kydex and Celtic for a leather/Kydex hybrid (for my P365's).

Thank you for the input everyone, very helpful, to say the least. Lots of help.
Has anyone improved the trigger? Seems mushy, might be the nature of the design. Glock has a lot of aftermarket, not so much with Sig that I can find.

Black Point Tactical for the holster. I put a curves trigger in mine, couldn’t get used to the geometry of the flat trigger.

I carry the standard 365 in a Vedder light tuck (IWB) and absolutely love it. In fact, even when I have option of carrying OWB, I still use the Lighttuck, it's that comfortable. I've got several Milt Sparks (including VM2), N82, Crossbreed, EP Saddlery and they are all great holsters. But I love the Vedder.

https://www.vedderholsters.com/lighttuck/

My personal observation is that the majority of the hybrids actually have the worst of both worlds. The leather is too soft and the plastic and other hardware are unnecessarily bulky. In fact, almost all of the plastic holsters I've seen lately are ridiculously bulky, the PJ holsters mentioned above being the rare exception.

Honestly, I see no reason at this point to buy any of the plastic holsters. It's too easy to design and make your own from thin kydex. All the components are readily available, and the only tools you need for good results are a heat gun, a drill, something for cutting (I use a scroll saw), screwdriver and/or rivet tools, and dremel. Making your own hybrid is just as easy.

I want to thank everyone for their input, appreciate it.
For better or worse, we shall see, I bought a Milt Sparks Summer Special 2, and PJ AIWB holster. Will try them both and pick one, maybe use both at different times.