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: https://ideatrash.net/2022/05/howto-secure-and-share-your-internet-on-free-wireless-wifi.html

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.

Flatpak can sometimes complain when there’s a symlink (Steam, in particular, does this) so you can use the symlink, but have to update XDG-USER-DIRS to point to the actual location. I wrote it up here: https://ideatrash.net/2024/07/howto-update-xdg-user-dirs-to-avoid-symlink-issues-with-flatpak.html