back up weapon / sometime primary weapon

starting down the road of procuring an ankle holster for a Glock 30.
what have you tried?
what has worked for you?

any general information for ankle carry also appreciated

The largest, heaviest pistol I ever tried to ankle carry was a Charter Arms .44 Bulldog.  This was decades ago.  I was able to successfully do it, but I believe that was right at the limit of what I could tolerate.
The Glock 30 is even heavier.  Maybe you can do it, I don't believe I could.
At my current age, I have given up on ankle holsters.  I can still see applications for young people, but eventually you will grow too old to use it well.

I ankle carried a BUG from day 2 out of the academy for the next 32 years.
I carried everything from a Colt Dick Special to a 2 inch Model 64(steel K-frame)to a Glock 26. The most carried was a 442 I bought in 1994.
Ankle carry requires a top quality holster, the correct pants length and width, a period of adaptation, and a defined mission.
It is not for everyone. Some people's build or tolerance will not work with it. Expect to pay well north of 75.00(closer to a hundred) for a holster...that you may not like.
It works best with small, light guns over the long term. I wore the G26 for about 4 years daily as a system with my Duty G19 and it started bugging my knee. That weight swinging at the end of your leg affects your gait and hyper extends the joint minutely . Over time, dysfunctions can arise and it's aggravated by the size and weight of the gun.
Weight and bulk also exacerbate the stability issue. The heavy gun wants to move up and down and rotate as you walk, scuffle or(especially) run.

The ankle holster sucks as a primary carry method. It is the absolute last choice for on-body carry, as in: ankle or unarmed. Period, full stop.
It shines as a BUG location, particularly from a seated or grounded position. So it works well in a vehicle for a surreptitious draw. Did that many times.

If you're new to ankle carry, a G30 is definitely jumping in the deep end of tolerance and concealment.

To help support the gun, ankle height shoes with padded collars are a real aid to stability and comfort. Calf straps help, but are another constriction point as far as comfort goes.

A secondary issue is security. Some thumb break designs in conjunction with autoloader slides are quite prone to being released during the course of moving around, bumping into things(even one leg brushing the other) or when the pants get constricted in certain ways. They also tend to print more.
Revolvers tend to have less of an issue due to the thinness of the hammer area. Conversely, the Centennial styles(442, 642 et al)  have a similar problem as the autos to a lesser extent.
My long term preference was a 442 Carrie in a Galco Ankle Glove with no thumb break strap. Instead, the sinus of the revolver grip allows the holster to secure the gun firmly with a rubber grommet. It's secure, fast, fumble free, cannot be accidentally activated and doesn't print.

If the desired use is as a BUG, I would emphatically advise against the G30, especially for an ankle newbie. An Airweight J-frame is the default Easy Button, and the gun itself has other advantages for the BUG mission that no auto can match at bad breath distance.

Edit to add: A couple of things about the mission that an ankle carried gun best fulfills. It doesn't serve as an extension to firepower, a'la a New York reload like a second pistol carried in a pocket or on the belt might. It doesn't really fill the "jammed pistol" transition either. Drawing from the ankle is slow and awkward from standing, especially as a reactive response. From covered kneeling, on the ground(or a staircase, as happened to me once) or seated is where it makes sense.
So the notion(that I subscribed to for the longest time) of having guns that share magazines or speedloaders is moot. The foreseeable circumstances of employing an ankle gun are scuffling, being mounted or a sneaky deployment from seated.
The first two are where a revolver's indifference to a fouled grip and the ability to shove it against your opponent and reliably discharge several shots are paramount. This far outweighs any concession made to shootability at extended ranges, volume of or sustaining fire, or even caliber.

Consider, drawing your primary weapon for threat management can happen a thousand times without the need to fire or the need to fire more than a shot or two.
Generally, if you have the need to draw your BUG even once...your are in Deep Serious. That's when nothing matters more than presence and reliability under all conditions, grips or positions.

Chuck Haggard (IIRC*) advised against an ankle gun that weighs over ~16oz loaded, that range. Supposedly once you hit 1lb or over, you're begging for joint issues on that side down the line, it's not an insignificant weight even if you can conceal it

Revolvers on the ankle: No mag button to somehow snag, resulting in you kicking a mag across the floor at the mall, all the ammo is contained in the cylinder

I totally read that as "Glock 30 cankle carry"

This 100%.
The weight of ammo in the mag is another factor in the stability of the gun on your ankle. Not a big factor with an LCP, but start adding ten 9mm or, God help us, .45s, and it adds a real lever to the fulcrum of the trigger guard.

yeah

Don't get me wrong, I think .45 is an awesome caliber, rumors of its demise, greatly exaggerated, if I had to pick 1 service caliber round to save my life it would be .45 HST

BUT, ~31oz loaded on an ankle is asking a lot. For ankle carry, guys can tell the difference between 13oz and 16.5oz loaded, what is effectively a duty sized gun is a big challenge

If I had to pick a glock for that duty and not a revolver, I'd say the G42 at ~17oz is within weight range, stays in the glock family/muscle memory, etc

G30 is big for normal carry. I would carry the g30 normally and get a smaller like LCP etc for ankle carry.

looking at other options