This thread is interesting. OP I think you have done the right thing (in the right way) if he is still meeting up with ex to discuss their relationship.
As for how is best, I think it totally depends on the context not just length of relationship.
On occasion I have done the text thing, or received the text and it felt like that was ok for each context, and we moved on. I also have two situations where things were quite different…
I was seeing someone for 7 months, and they sent a blindsiding text (citing external factors). No way was that acceptable, I went to see him and we had a proper conversation. That gave me closure and also hopefully he learnt that a text isn’t respectful after that length of time. And that it is it possible to talk it through as grown ups, still end the relationship but having given each other space to talk.
On the other hand, I was seeing someone for 4 months or so but it was quite intense. Whole weekends together. He ended it by phone, but some of things he said were quite hurtful (essentially laying it at my door) and so for closure in that instance I wrote to him, and briefly explained the impact that sort of framing can have. We have since talked it through, I believe in a dignified and mature way.
In both situations, if I had simply sent a ‘thumbs up’ emoji or blocked him after the call, none of us would have had closure, or learnt anything.
I think my point is, in both the two detailed situations they were with men who were decent, emotionally articulate (not the same as emotionally available) and not dicks.
Two different courses of action, in different contexts, but both of which resulted in adult, mature conversations where we can away with respect for another’s perspectives and emotions.