This is the first deployment of R80.20 so i may have missed something unknowingly. I had Radius working previously since R75 but had to add the local accounts for radius to work. This was resolved in R76 i'm informed 🙂
I have the following set on my Radius profile.
CP-Gaia-SuperUser-Access = 1
CP-Gaia-User-Role = "adminrole, radius-group-any"
output from /var/log/messages
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t -volatile:mrma:users:user:USER123:pid 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:pid 3425 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:pid:3425 USER123 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:ppid:3425 0 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:access_mechanism:Web t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:access_mechanism:CLI t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123 t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:"adminrole t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:"adminrole:domainname:default t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:radius-group-any" t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:radius-group-any":domainname:default t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:radius-group-any t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:role:radius-group-any:domainname:default t 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: nobody localhost t +volatile:mrma:users:user:USER123:su t 
Dec 4 15:24:21 2018 Gateway1 httpauth: pam_radius_auth: Non local user 'USER123' will be in 'superusr' and have root access
Dec 4 15:24:21 2018 Gateway1 httpd2: HTTP login from 10.76.0.26 as USER123
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: USER123 localhost t +webuiparams:logincount:USER123 2 
Dec 4 15:24:21 2018 Gateway1 xpand[12675]: Configuration changed from localhost by user USER123