Hi all i got a notification to join the beta testing programme this morning at 3.00 am .... your handset has to be CARRIER /NETWORK /SIM FREE .
Once I registered I tried settings-about phone-software update several times and just downloaded a 1.463gig update to containing Android 8 / Samsung 9 exp.
I've got and downloaded the beta update.
I found this registration in my notices and had to click the beta photo and scroll down to register.
Not been able to check it out fully as working but will update you later.
After going to Samsung members and signing up to the Beta. You have to go to setting and update manually. Can take a while for it to show up. Like it did me. What I ended up doing was restarting my s8+ then reloading members. when I clicked on manual update it was there. Hopefully this helps