The sentence shows a specific ability not a general one. 'Could' is not used for a specific ability in the past so we have to use 'to be able to'.

'Can' doesn't fit grammatically as we already have a modal verb (will) plus verb (allow). The infinitive 'to be able' does fit. We can only use 'can' for the future with a time phrase e.g. 'I can come tomorrow'.

'Could' isn't possible as it's the present tense for something that's always true, not the past. 'Are able to' also fits.

We use could + have + past participle to express an ability in the past that was there (playing the piano) but for some reason, never got fulfilled (she never had lessons).

The sentence shows a specific ability not a general one. Only 'couldn't' is for specific abilities in the past, not 'could'. 'be able to' can be used though for a specific ability.

It could be any, depending on the context. If we are talking about the present, both 'can' and 'is able to' fit. However, the statement could, for example, be someone talking now about an artist from the past, in which case 'could' fits.

Either of these can be used to talk about present ability.

It's talking about the past.

It's about something the person wasn't able to do, so it's couldn't.

This is about what everyone is able to do with modern communication tools at the current time, so it's 'are able to', which reflects what can be done in the present. Using 'could' would imply possibility rather than ability.