Certainly there are descendants of Celtic people throughout Europe, but they don't know it having been conquered by Eastern barbarians.
The jury is out on the Germans being just a different tribe of Celts, but the fact is their coloration is different. Now that's somewhat obscured in modern populations due to the population rebuilding efforts after the 30 Years War where numerous Irishmen and Bretons volunteered to help the German ladies have babies, but it's pretty clear the Germans are really different!
Gaelic speakers are known to have been at large in the Mediterranean previous to 700 BC, and resident at Troy for at least 1000 years prior to the arrival of the Greeks on the scene. They had a culture and civilization coincident with the first stirrings of serious civilization in the Levant. I read your site where you seek to turn Gaelic speakers into the "Lost Tribes", but you wait until 610 BC. The known dates for independent Gaelic civilization are much older than that and must be respected.
One of the prophets does note that David has in his ancestry a Scythian, and the Scythians at that time are Celtic. I'd rather think that's how Gaelic speakers ended up among the Semitic speaking Kurds occupying Palestine in the old days - they showed up in a boat and visited the ladies - nothing need be more complex than that.