volte US version in at&t roaming with windtre SIM
I'm in US with only AT&T roaming coverage and a windtre Italy SIM in the phone and I would like to be able to receive SMS once again in roaming like I did for the last 20+ years.
The Zenfone 8 is the only phone that fit my needs and is supported by LineageOS latest version and is present in the most recent windtre list of volte supported phones and in the at&t HD voice (volte) supported phones as well.
Only the US version of the zenfone 8 supports all LTE frequencies of mintmobile for my US SIM card so I need the US version, not the international version.
I've two questions:
1) does the latest zenfone 8 firmware update of the US version of the zenfone 8 also include the volte software support for windtre volte, or is only the international version with the windtre italy telco volte support?
2) because I cannot change the SIM (and it's several years old), do I have a chance to get volte working on the windtre nanosim over at&t roaming by just plugging it in the zenfone 8 (US version)? Or is it impossible to fix volte without upgrading the nanoSIM first?