On current releases, you migrate form 1Xp to User Portal. Not as nice as 1Xp, but still has the web rtc option. For remote workers, you can use an SBC, but you mUST secure the system none the less. This means certificates, TLS etc. If you arent familiar with certs this gets pretty tough if you have never done it.
IPO CAN work with teams, wether just a dialer or direct routing integration. ACO deos as well but easier setup and no infrstructure.
ACO makes all the remote stuff easier.
Either way Avaya does have DaaS which is Device as a Service. This gives you Opex pricing for the phones and can roll that into a monthly cost with ACO, so no upfront which helps with the devices.
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