"Relatively" modifies "recently" as an adjective. Recently means "not long ago", and "Relatively" doesn't actually change this meaning a whole lot; it just emphasizes that it's close to present time on some imaginary timeline. You'll hear "Fairly" or "Relatively" used for this. "Until" tells you that something changed (or changes) at some point in time. What time? Not very long ago! So, "Until relatively recently" = something changed not very long ago. Maybe yesterday, or a few weeks, or months ago, but if you look at the timeline it had been the "old way" for a longer time! Timeline visualization: -------------------------------------------------------------------------< change > ++++

Until means till then, say , He stayed with me until his mother called him. Relatively means in relevance to. Recently means lately,say, He has changed a lot recently

Relative to a previously mentioned event (or now if none mentioned), up to that point in time.