In the last few months, two US amateur radio stations have applied for and received special experimental callsigns for the 40-MHz band. Lin, NI4Y near Atlanta got the call WL2XUP while John, AE5X in Houston got the call WL2XZQ.
The application form 442 from the FCC is called an Experimental Radio Station Authorization and it costs €125 for two years.
AE5X has a page up on his blog now with guidelines for US stations interested in applying for a permit. Go to http://ae5x.blogspot.com/p/operating-on-40-mhz.html
While the Summer Sporadic-E season is pretty much over for now, there is plenty of time to get ready for when it starts again in May of 2022.
For more information on the 8-metre band, see my 40 MHz page HERE