Do you think a 22 conversion has any training benefit?

Glock 19 / AA conversion is specifically what i'm talking about.

I have had it for several years and shot it a bunch when i first got it to test it.
Mostly it just sits especially now that i have a suppressor it's always the buckmark i shoot suppressed.

If your EDC is the Glock and you're trying to save some money, yes. But, fortunately, 9mm has gotten so cheap (not as cheap as .22) that I feel pretty good about sending rounds downrange. And, I know I need to practice shooting with some recoil. Just hoping the price on .45 keeps coming down, too.

Like you, I tend to shoot .22 out of suppressed hosts now.

I reload 9mm and shoot it for USPSA pistol and PCC... a local indoor range I shoot at has a no reloaded ammo requirement, and I typically choose to obey their request... my G34 and Advantage .22lr upper gets used at that range a lot... one shot only from low ready, and alternate weak and strong hand

I train my 11 year old on a G17/AA combo. He loves the M9-22 more but doesn't like Mystic X making it too end heavy. So yes I see a benefit to the conversion.

I shoot 22 conversions more than their centerfire counterparts.  I shoot Glocks mostly and have several Advantage Arms 22 LR conversions with dedicated frames.   I also shoot my dedicated 22 LR AR-15's more than my centefire AR's.   I reload so I shoot 22 LR so I don't have the hassle of trying to recover my brass.  I like to shoot my AR-15 dedicated to 22 LR for CQB drills on steel targets.  I have a 50 yard range at my house and shoot a lot at my range.

I have very good reliability with my AA kits and my dedicated 22 LR  AR's are reliable unless I get a bad batch of 22 rimfire ammo.  I've taught more people to shoot using my AA kits and 22 conversion or dedicated rimfire AR's than any other guns.

One benefit of conversions that doesn't affect shooters in free states but does in anti gun states is that the conversion kits are not regulated like firearms. Many shooters will opt to buy a kit to shoot 22s instead of jumping through hoops of registration, waiting periods, etc.

They're fun but can be finicky.

I have a kadet for my cz and use it all the time.  Use it both suppressed and unsurppresed. I love it.

I had a Marvel .22 conversion for a homemade 1911.  It was remarkably accurate and never jammed.  Wish I still had it.