https://www.music-map.com/ can help a bit. It knows surprisingly underground bands.
Random browsing on Bandcamp can produce results too.
Depends on how progressive you want to go, as when you are bordering on noise, ambient and other fringe genres, there are lots of bands with little fame.
I have a single album from “Lento” that is pretty cool. Post-rock, powt hardcore, post metal kinds stuff.
Nero Di Marte is on the more extreme side, but flirts with prog.
Oranssi Pazuzu is prog and black metal together. Weird stuff, but good.
And a long time favourite: Circle. Lots of different kinds of albums, most pretty great. Awesome if you can catch them live.
Edit. More stuff and typos
There’s this noiserock/prog group called Fushitsusha. The songs are long, winding and sometimes grinding romps. They have some traditional Japanese elements mixed in as well.
If you don’t know about Mono, go have a listen. Especiall Hymn to the Immortal Wind. Stuff brings tears to my eyes.
Onnittelut on paikallaan, sillä tuotteer on kohtalaisen laadukkaita. Näiltä neljä pakettia hankkineena ei ole tullut katumusta päälle, mutta toisaalta en ehkä enää viidettä menisi hankkimaan.
Archetype sarjan plugarit, varsinkin Petrucci on todella monipuolisia leluja jotka teki kotikitaroinnista aivan ykkösharrastuksen. Saundeja löytyy satoja, on efektejä ja vaikka mitä mukana. Varsinkin jos malttaa black fridayn aikaan ulos puksahtavaa -50% alea vartos, on hinta/laatu oikein kohdillaan.