Anything that would indicate ADSL or VDSL. Attenuation would do as well.
Event log?
Which router is this?
This is a Plusnet Hub one router.
The event log seems to suggest it's still ADS! This is the log from its first startup this morning and it shows WAN as ADSL
( 196.890000) NTP synchronization start
08:47:52, 23 Apr. ( 195.390000) WAN operating mode is ADSL
08:47:51, 23 Apr. ( 193.970000) PPP IPCP Send Configuration ACK
08:47:51, 23 Apr. ( 193.970000) PPP IPCP Receive Configuration Request
08:47:51, 23 Apr. ( 193.660000) PPP IPCP Receive Configuration ACK
08:47:51, 23 Apr. ( 193.640000) PPP IPCP Send Configuration Request
08:47:51, 23 Apr. ( 193.640000) PPP IPCP Receive Configuration NAK
08:47:51, 23 Apr. ( 193.560000) PPP IPCP Send Configuration Request
08:47:49, 23 Apr. ( 191.800000) PPPoA is up -​ VPI: 0, VCI: 38 Down Rate=18981Kbps, Up Rate=1084Kbps; SNR Margin Down=3.3dB, Up=7.4dB
08:47:49, 23 Apr. ( 191.790000) CHAP authentication successful
08:47:48, 23 Apr. ( 190.960000) CHAP Receive Challenge
08:47:48, 23 Apr. ( 190.960000) Starting CHAP authentication with peer
08:47:48, 23 Apr. ( 190.960000) PPP LCP Receive Configuration ACK
08:47:48, 23 Apr. ( 190.940000) PPP LCP Send Configuration ACK
08:47:48, 23 Apr. ( 190.940000) PPP LCP Send Configuration Request
08:47:48, 23 Apr. ( 190.940000) PPP LCP Receive Configuration Request