test again:
nostr:nrelay1qqdhwumn8ghj7mn0wd68ytndd94k2erfd3nk2u3wvdhk6tcqr3mhxue69uhkummnw3erytndd94k2erfd3nk2u3wvdhk6tckn0l55
Discussion
I see it on Damus. Not sure what your testing. ❤️
Does it render as links to relay URLs or as as nostr url string with no particular meaning?
As far as I can tell, just text. 
Ok. My first test wrongly used TLV type 1, which is why it just looks like a long nostr url with no meaning.
My second test used the correct TLV type 0, which is why it pulled out the relay URL. Looks like only the first URL is rendered. (And I don't know why nrelay1 is TLV, I presumed you could add multiple URLs).
So Damus supports it, to a degree.
I added support for this in Damus, but only did the decoding part of it. At that time (maybe different now) Damus didn’t have seem to have a simple way to make relay URLs interactive. Would be nice if you could tap and then have an option to add it to your list of relays. But currently it just shows the URL
It is the same story in gossip currently. It just renders the url, but it's not clickable into anything (there are no wss:// handlers), and I plan to make it open the relay configuration page for that relay (which we don't have yet as a separate page, so of course I can't do that yet).