You could try using a relay somewhere in your process; while I was on a travel gig I had to do some finicky work with a travel router (though this may not work, since you need a VPN for your work, but maybe it’ll give you an idea: ideatrash.net/…/howto-secure-and-share-your-inter…

Also if you have your DNS resolvers manually put in, you may not encounter their portal. Had that problem when on hotel wifi as well.

All that said, I ended up using phone data a lot.