Alternative hangboard mounting ideas?

I have a hangboard but no way to mount it. My door does not have any trim, so an over-the-door pull up bar does not work. And I don't have any studs above my door. Any ideas on how/where to mount a hangboard? 

Could you hang it from a tree branch?

If you live in an apartment complex and have stairs, this is pretty easy:

Buy a 4 ft section of 2x10 (or 2x8 or 2x12)
There WILL be studs along the outside edges of the door - roughly 3 inches in from the door opening - going all the way to the ceiling. Those are the king studs. (look up "how to frame a door")
Sounds like yours just doesn't have any cripple studs put in. You'd wanna span out to the king studs anyhow typically.
In the framing diagrams that come up- they DON"T show the roughly 3/4 inch thick board of the door frame that you actually see. That's floated inside the jack studs with shims.

Screw your 2x10 to the king studs you find- - - -then screw your hangboard  to the 2x10
Just make SURE you find the king studs. There are some really wild hack jobs out there where people framed stuff up quite insanely wrong and your door may be one of them. But 99% of the time this is how it will be.

(actually here's a picture)

I built a seperate frame in a N shape and i clamp it to the door. No fuss, no damage.

any picks of the frame? i dont want to drill in a rental but i'm not going to the gym while COVID numbers are climbing

Drill in your rental. Spackle is cheap.

Ideas/inspiration, maybe you can find something that will work for you in here:
https://www.beastmaker.co.uk/pages/your-setup

Some ideas here, I particularly like the last one where they built a frame inside their door frame, no trim or drilling into wall needed I think
https://www.beastmaker.co.uk/pages/mounting-your-fingerboard

But also what Sean said seems standard, using the king studs, should work on almost any wood-framed door if you're allowed to drill.

I've seen a hand board held up with two pieces of plywood on both sides of the walls and were help by C-Clamps.

Someone I know purchased pull up stand from Amazon and attached hangboard to that
https://www.amazon.com/dp/B00HYQP72O

Another alternative is to make a French cleat back board

Advantages:

• it’s compact - board can be left up or taken down and stowed behind the door.
• Easy up, easy down
• made from readily available inexpensive wood materials 
• It can be made tall enough to mount most small-medium sized hang boards, or you can custom make an arrangement with holds/campus rails like I’ve shown here (as shown it's 30" wide x 5.5" tall)
• bonus - you also have access to the back side of the board where additional screw-on holds (up to 2-1/2” deep) can be mounted without interfering with the door
• bonus #2 - you can have multiple interchangeable boards 

• 4 small screw holes in the doorway casing that would need to be filled if removing the system. Small price to pay IMO *
• if you make it over 8" tall, people over 6" will need to remove it or duck to get through doorway
• A DYI project - not available commercially unless someone starts making and selling
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  * Or you can use the old college trick of just using toothpaste if trim is white (you didn't hear that from me). I put one of these up downstairs in the guest bedroom doorway and my wife had a fit. So I moved it upstairs to my office doorway. It was quite easy to patch...the right way...with a little wood filler and paint.

Blue Collar Climbing wrote: Drill in your rental. Spackle is cheap.

indeed but my lease is stingy 

I just built this. It gives me enough room over head to do a high pull up yet still enough room under it to walk without ducking. Also it’s removable and interchangeable with other hangboards.