@Moriah8
Hi- hope you are well.
I think it comes down to cultural differences. In Europe we generally don’t give tips even at restaurants as it’s usually already included in the overall bill- personally this is very much an “American” thing, it’s not viewed in the same way here.
As mentioned by others here it can also be received with some awkwardness- I think unless you are staying in hotel listed on Airbnb then better to avoid.
When I stay in a hotel I leave a tip for both management and cleaners but in a private home I leave a thank note/card with some chocolates or something. I believe this is probably what you are getting with your international guests.
Overall, I think if someone wants to thank you with whatever it may be- a simple and gracious thank you is enough. If it was given in the form of money and this does not suit well with you then there are plenty of charities etc who would be very grateful. No awkwardness is needed, especially where kindness is involved.
Have a beautiful day!
Yadira 🙂