Moving to Fibre - SIP/VOIP app for mobile phone

Edit: I have reposted here: https://forums.thinkbroadband.com/voip/f/4749059-mov... as suggested and would prefer to discuss on the new thread.

I now have Fibre available and while I am looking at keeping the landline, I am not that chuffed with Digital Voice, which seems only to be available with BT Broadband and their router, or with a lot of messing around with an Analog Telephone Adapter [ATA] and apparently no legitimate full VOIP solution for residential customers. Overall, I think with the radical change in technology, it is time to go for a full SIP/VOIP solution and eliminate ATAs, ie bite the bullet and avoid hybrid technology.

A further reason to go fully digital with the landline is that I intend to use the runs for the extensive PSTN to put in ethernet. So what I am planning is a small PBX, eg on a Raspberry Pi. I already have a SIP/VOIP phone working and I have a couple of 4 year old Android phones [Android 10].

So does anyone have any recommendations for
[1] SIP/VOIP apps which I can use to play around with this? Note that I need an app which is not hard programmed to any VOIP provider.?
[2] Any SIP/VOIP PBX software for Raspberry Pi?

[3] And can anyone tell me if I am wrong about it not being possible to have Digital Voice fully digital in the house?

Any and all help appreciated

Edited by DFScale (Sat 16-Dec-23 09:08:36)

There's a specific VoIP board here, may be worth posting directly there.

For apps, I use Groundwire which I may have paid a couple of quid for years ago. It appears quite 'professional'. I have iOS but assume it's Google too. [Edit: It does]

Thanks for that, Woolwich, I have reposted.