Most of my holsters are Kydex but I do have a couple of hybrid kydex-leather holsters that I like to wear from time to time.
I was thinking of purchasing a new all-leather holster to see if it would be more comfortable (I carry IWB 3 o'clock[ish]).
After I clean my guns (P365X, G43X) I usually give the slide a quick light wipe of oil for esthetic purposes.
Is that a bad idea for a leather holster?

Light oiling on slide w not damage leather.

That's good to know.
Thanks!

Oiled guns and leather holsters have been going together much longer than any of us have been alive without issues.

Being honest here. I used to use plain old Dino oil to oil my knife sheaths (only made a few for my own use as a kid). The knife I still have, the sheath is still in excellent shape. It’s somewhere around 50 yrs old.  I wouldn’t worry about a few drops of oil.

Wow!
I wish I still had my Dad's old fishing knife.
It had a beautiful leather sheath and he kept that blade razor sharp.

It's not an issue that I've seen. I use a leather ankle holster for a backup and wipe my P365 down with Ballistol every once and while as it's exposed to the elements and SIG doesn't use the most rust resistant finish on the P365 and mags. Never a bit of rust. I would advise against having the gun completely saturated as it tends to attracted dust and debris more easily. Wipe down with a clean, old t-shirt after oiling leaves enough on it to protect.

Ballistol, which AFAIK is namely mineral oil, is advertised as good for leather.

So far I haven’t had an “issue” with CLP, motor oil, or Ballistol. My eldest leather is hardly 10 yet, but that’s still a decent age where you might expect damage to become apparent.

When I do a deep clean, I use a leather conditioner for shoes. Seems to be ok. I’m sure a neats-foot or other common boot oil would work great. I have Red Wings that are more than a decade old and the leather is still in good condition, oiled every other month or so.