I didn't really know what a steward was supposed to be, so I accidentally made my housecarl the steward in Lakeview Manor. By the time I found out that I made a mistake, too many gameplay hours had passed so reloading an old savegame is not an option anymore. Is there any other way, perhaps via console commands, to 'un-steward' my housecarl, or am I just gonna have to live with it, literally?

Been trying to find this out myself, I did the same thing.

You can kill them and go get another steward, but the Jarl will not be offering you another housecarl. I would not consider making the housecarl your steward a mistake anyway, just means you have one defender less than you could have had.

Q: Is it possible to change the steward?
A: Wouldn't it be better to hire a steward who was potty-trained?

Sorry. Couldn't resist.

probably safer to use one of the low level npc like faendal.
as a bonus, you get hs house in riverwood, permanently 8D
and you steal camila valerius.

This is confusing

I have him as a steward in Hjaalmarch and Faendal keeps talking about Riverwood and Camilla, but he doesn't wander back there (like Valdimar probably would do). I keep hoping he'll bring Camilla by the house for dinner, but no such luck.

Rayya is my Housecarl & I too made the mistake of making her my steward. Another fighter in the household is always good. Anyways my house came under attack and everyone started defending it. Rayya got killed. Found her corpse near a bush. How the heck did that happen? I thought Housecarls were un-killable & just fall to their knees for a while? Or is that only Lydia?

So I cheated by using console command to bring her back to life. Here's when the game totally bombed. Shortly after I brought Rayya back to life, I used the setessential console command to make her invincible. When I turned around, her corpse was missing. Ok never mind I thought, after all I did bring her back to life right? So I go patrolling only to find another Rayya around the corner. Yup, I now have two Rayyas. Both are Housecarls and stewards. WTH??!!

She had a twin sister in Hammerfell.

I made Lydia my Steward, but she keeps going back to Breezehome. Unless, I make her my follower, then the Steward options dialog disappears. ???

Valdimar is my housecarl up north and he's always there. Sven asked me if he could be my steward so I let him and now I'm without a follower. I'm lonely. Next follower's gonna be a girl.
For now it's me and my horse with the red eyes. LOL