Thanks for your replies.
No docker since im running on ARM cpu.
I also tried the community package, and it was bugged on my unit. Script check worked, and i found movies from my rss links. but no series.
What i did was install chroot from the community package repo. After that i made a normal Flexget install. And mounted volume1 in chroot to have flexget check destinations and so on.
After that i made a startup script in /usr/local/etc/rc.d/.
with this content:
case $1 in
chroot /volume1/@appstore/debian-chroot/var/chroottarget service flexget start
chroot /volume1/@appstore/debian-chroot/var/chroottarget service flexget stop
echo "Usage: $0 start|stop|restart"