I am also interested in getting more 30 day + bookings. We have had a lot of success finding these clients on Airbnb. If you are only interested in 30 day or longer stays, you are able to set a 30 night minimum on your Airbnb listings, and that should help you filter out from being seen by shorter stay guests. Have you tried that?
We still like to fill in small gaps, with short stays, so we are still a 1 night min. However, using pricelabs, and our unique pricing strategy, we have many of our homes that are available to be booked by 30 day + guests with very little advance notice. The key is preventing shorter stays from booking, so that your have long gaps of availability in your booking calendar. One of my favorite bookings we got this year was a 45 night stay, that was booked 1 week in advance of the check in date. I have found that those guests are willing to pay a higher nightly rate because they are desperately looking for a place to live, and 30 days at one of our houses, is way cheaper than 30 days at a hotel or other short term rentals.
There are more and more platforms popping up all the time to list 30 day + rentals. To name a few on top of the ones you listed:
Furnishedfinder
30DayStays
Homads
Homefornow
Xome
ect.
As @Paul Sandhu will tell you, I think there is still a lot business that can be conducted using Craigslist as well.
I also have reached out to Hospitals, universities, and large local business, to let them know of our available properties if they should have a client who is in need in the area.
I think it depends on your market, and your target audience as to where is it best to find mid-term renters, but I think this is a market that will continue to grow and develop as more and more people decide to move around more often, work remotely, and work on short-term job contracts.
Cheers,
-Benjamin Vail