I don’t really know where my favourite bands fit in here or even if they do but most would probably consider them obscure. There is a group of 6 bands who are:
The Dark Element (Finland/Sweden)
Panic Room (Swansea)
Mostly Autumn (York)
Karnataka (originally Swansea)
Within Temptation (Netherlands)
Nightwish (Finland).
They have no UK chart history whatsoever between them, zero UK daytime radio exposure, most on here will not have heard of any of them and none of them has played at let alone headlined Glastonbury or Reading (although Within Temptation 2005 & 2015 and Nightwish 2018 have both headlined the Bloodstock Festival). So they do meet all or most of the OP’s obscurity criteria but does that actually make them obscure? It would seem that most (but not all) of the genuinely obscure artists already posted here are obscure by virtue of the fact that they were very short lived acts from the 80s/90s/00s some of whom left behind some extraordinary items of work but these 6 ‘obscure’ bands are all still currently active and, apart from The Dark Element (which is more of a collaborative project than a band) who started in 2017, they have all been around for quite some time, Panic Room since 2007 and the others since 1997/98. I always go and see any of them live whenever and wherever the opportunity arises and I have more than 50 CDs/DVDs of their combined output and still counting so in the longevity and output aspects, they all differ from the genuinely obscure bands.
Anyway, there are plenty of videos of all of them on YouTube but I won’t post 6.
https://www.youtube.com/watch?v=bipnYwpreqs
https://www.youtube.com/watch?v=SZsuGtv3-co
https://www.youtube.com/watch?v=lTvYfLa4Wlk
