Anyone here know how to fix it temporarily?
Are you sure it doesn’t have a S or P bend under there? Since floor drains often only get water down them once in a blue moon there is a possibility there is a trap but it’s dried out to the point it lets smells waft back up the pipe.
If it really doesn’t have a trap and you aren’t interested in installing one yourself the least effort option is to tape over the drain outlet until you get it fixed.
No S or P, unfortunately. Is there a easy DIY video on how to install P trap? The issue is its tiled floor and I dont want to break the tiles and dig
Can you access the pipes from underneath the house or are you on a concrete slab/other without access?
Had a similar issue and found a “Geruchsverschlusseinsatz” what helped - roughly translates to “odour trap insert”. For the diameter and depth in my flat back then this was fitting: https://www.dallmer.de/de/produkte/482013_Geruchsverschlusseinsatz-zu-TistoPlan.php#anchor_897ac650_Accordion-Datenblaetter-und-Ausschreibungstext
It’s in German but when you scroll down you can switch to English (but at least on my mobile I only get to the Home page then and not to the product anymore)
Call all the plumbers