@bmc I don't understand why you keep asking @Archer to contact all of these ISPs until an unwitting sales bod happens to give an answer you want to hear, when the chances are that the 'positive' but wrong answer is the typical uninformed non-technical sales response (to get a commission payment for a sale), and @Archer might end up with a non-working solution tied to a long term contract from which they can't escape, and in the mean time will have lost access to Plusnet email, and the ability to use a landline phone.
Summary -
- Plusnet - don't provision SOADSL and require a phone service in order to continue providing ADSL, therefore when the PSTN phone switch-off occurs, the phone line disappears, which in turn destroys the ADSL broadband account, which ends access to Plusnet email, referrals, webspace, etc.
- EE - don't provide either ADSL or SOADSL, so not worth exploring phone options.
- BT - is unlikely to be able to provide working "digital voice" on an SOADSL line - because of limitations in their router. However they probably can provide broadband only via SOADSL, and at some unspecified time in the future might be able to provide a phone service using "SOTAP for Analogue" if an additional ADSL landline master socket is installed in @Archer 's home, and running (and paying for) two separate connections all the way back to the telephone exchange.
FWIW, A&A can provide SOADSL and VoIP - but VoIP over SOADSL would require @Archer to source a QoS capable router, but it could probably be made to work.
Rather than trying to find a less than desirable ADSL based solution, if a faster broadband solution could be found, such as satellite, mobile 4G/5G, "fixed wireless", or AltNet fibre network, then any of those would be a more future proofed solution, and have a much better chance that the wanted landline number home phone could be successfully migrated to VoIP.
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