Yep - many here have. Suggest a search for "fel boom pole" Some built are dedicated FEL boom poles , and some attach to a bucket.. Maybe more builders will chime in.
I made one yesterday for my mini-skid steer to help set power poles. It's a bit smaller than the size that you need but the boom is 1-1/2" sq tube 10' long and I welded a couple of fittings for it to attach to the back plate of the pallet forks attachment. With the 6' lift of the mini and the 10' height of the boom I should be able to lift a 20' pole high enough if I hook it about 6' from the top and put it in the hole.
The mini will lift 515# and I'll use a small block and tackle attached to an eye that I welded to the top. The boom will have to be vertical to get the pole standing and then I can lift it from there and move it to the hole.
If you don't want to make one, you can buy them too. Millonzi makes one (photo) that attaches to a universal QA. I think I paid about $350 plus shipping. The boom is made of 2x2 square tube and there is no risk that my loader will overpower it.
I made a boom pole for my B7800 using a simple 2" receiver hitch reinforced to the bucket. It can be extended to lift light items like trusses. I have since painted everything orange to match the rest of the tractor. I will attach my forks attachment also. I use the receiver with a set of chain hooks most of the time.