No difference on 3internet either. So that's x3 APNs tried. Router rebooted each time. Upload is gimped on Three/Smarty with VPN usage.
Ordered a Voxi (Vodafone) SIM to try next.
When you say you tried it "on mobile" are you meaning with the simcard in the mobile phone, or is the mobile phone connected via WiFi to your 5g modem?
It makes no sense if it's on wifi going through the exact same hub :/, I'd start looking at device specific configuration or pointing fingers at the VPN if you know the connection will do it on some devices?