Talkatone http://www.talkatone.com
TextNow http://www.textnow.com - also offers mobile service, similar to Republic Wireless
GrooveIP https://snrblabs.com/GrooVeIp - Android only, limited use for free
Visual voicemail and robocall blocking
YouMail https://www.youmail.com
My Visual Voicemail https://play.google.com/store/apps/details?id=com.vna.service.vvm
CallControl/EveryCall https://www.callcontrol.com/
Truecaller https://www.truecaller.com/
Should I Answer? https://www.shouldianswer.net/
Nomorobo http://nomorobo.com/ free for (some) voip lines
Hiya https://www.hiya.com/products/app recommended by AT&T, freemium
supposedly useful in flashing phones to other carriers
$5/month as of 2023
includes the back cover
Decent screen size, NFC, card slot, $140 unlocked at Best Buy.
Can't tell if Proxoid works on Linux clients.
Free version transcribes the first 10 voicemails a month. Still requires conditional forwarding setup like YouMail, but reviews pretty well.
Samsung Moment (Sprint Android w/keyboard) on Cricket