Outlander Gaelic

[OC Richard]

A bit like those who claim to speak Cornish?

Not sure what is meant here. The corpus of Cornish is quite large, and anyone who has studied it knows how to pronounce it. Any such person could read any of the thousands of surviving lines of Cornish and be speaking Cornish.

If you mean conversing in Cornish, I met a linguist who is equally fluent in Welsh, Breton, and Cornish. Whenever he meets another person fluent in Cornish, well, they can converse as well and you and me in English.

[The Q]

The last true native speaker is believed to be John Mann who died in 1914, anyone since is a learner. Yes the written language is available, yes there are those enthusiasts who have learnt the language, but in reality it's a dead language not used in day to day use.
Much like Latin outside of the church or the fossilised Latin taught in some schools it's there, it exists, but no longer lives or develops.