It works fine on my iPad on 1.9.1 in Safari (on a ER-X-SFP). The UI is slightly smushed but works fine enough.
Are you by any chance using https with a self-signed cert on the edgerouter? I found that Safari didn't deal well with that even after I approved the cert. I ended up setting up my own CA and importing the CA profile into the iPad (so all my devices certs are now approved). Safari worked fine after that. YMMV.