TWRP custom recovery is now available for download for the Samsung Galaxy Fold 6. This will allow you to install third party firmwares on it. Before you flash it, there are certain things to be kept in mind. First, only the variants ending in SM-F956BXXX are supported and you ought to be on stock firmware before flashing it.
Also, you must install USERDATA AIO as otherwise you would not be able to install ReC.
Installation Orange Fox Recovery from TWRP or older ReC
1) Download the three files OrangeFoxXXX.tar, OrangeFoxXXX.img and OrangeFoxXXX.zip. Save files to the phone’s internal memory.
2) Turn off the Fold 6 phone.
3) Reboot into TWRP Recovery on your Fold 6 phone via the combo Phone Off + USB TYPE C cable connected to PC + Power Off Button + Volume Up Button.
4) Once TWRP is loaded, press Install.
5) Find the file OrangeFoxXXX.zip and flash Orange Fox Recovery.
6) Once finished return to the TWRP main menu.
7) At the end go to the advanced restart menu of TWRP and restart in Recovery mod.
8) Orange Fox should be loaded.
9) Reboot to the system on your Samsung Fold 6.