A glance at pre season 19 Bosman allocations appears to show:

9 were GK
1 was SW
14 were DF
13 were MF
3 were WG
8 were FW

I searched this forum and found 3 seasons ago stat:
start S16
GK - 7
SW - 2
DF - 11
MF - 14
WG - 2
FW - 12

Pre season 20 Bosman position picks

GK - 7

SW - 1

DF - 14

MF - 13

WG - 5

FW - 8