DrForinor - the reason why it smells is simple: bacteria build up, organic decomposition.
You have to wash the cloth every day: you don’t need to wash with soap - you just need to make sure you wash away all the milk residue from it.
I have a very small piece of a sponge cloth sitting by the machine, like maybe 10cm x 3cm.
I moisten it with a purge from the steam wand. I go about my routine, make my flat white and then clean the steam wand with it. After that, I purge the steam wand.
When I’m done drinking the coffee, I rinse my PF and basket, and also rinse - you have to rinse it thoroughly, and really well under running water - my miniature sponge cloth. I then squeeze all the water out and leave it sitting in the drip tray, and it’s dry next time I use it. No smells.
I’ve been doing this for years. Every few months, when the cloth wears out a bit, I cut another rectangle on the sponge cloth.
You can see the green rectangular square sponge cloth here: https://coffeetime.freeflarum.com/d/279-lelit-mara-vs-elizabeth-cleaning-and-maintaining/18
I used to have a yellow one for the shower screen. Same principle. But recently I’ve been using an aeropress filter on the shower screen, which means the shower screen is immaculate afterwards, without the need to clean. It’s overkill though, but I bought a box of aeropress filters so I might as well use them up! I don’t have an aeropress! 🤣