I followed Jason's video I just did on my PI-4 and it worked fine. The most important part is :
FLRIG, navigate to Config>Setup>transceiver.
On the configuration page choose your Yaesu rig from
the top drop down box labeled rig. In the next box, choose
"/dev/rfcomm7" which will be near the bottom of the list.
If /dev/rfcomm7 isn't found in the list, you can enter it
manually in the box.
N3VMT