ui: Unable to download files

Reported by dalaeance (using Vivaldi browser) at https://discuss.freedombox.org/t/solved-kinda-downloading-openvpn-profile-is-either-very-slow-or-nothing-is-happening/1284:

• FreedomBox is plugged into a router
• I’m running Debian GNU/Linux 10 (buster) and FreedomBox version 20.20.1.

I’ve tried, multiple times, from multiple devices, to download my OpenVPN profile. The circle on the button just forever-loads. I know the file is only a few KBs large, so what could be causing this?

I’ve succeeded in downloading the profile before, but have no idea how. The forever-loading has been a consistent problem since I got the box (in late 2019, I believe).

Tested with Chromium v83:

• Downloading the openvpn profile fails with the error message on the console: Download is disallowed. The frame initiating or instantiating the download is sandboxed, but the flag ‘allow-downloads’ is not set. See https://www.chromestatus.com/feature/5706745674465280 for more details.
• Trying to download the backup file opens new tab and nothing else happens