Maybe have a look at:
Commencal bikes
or
bike-discount.de selling Cube and Radon frames for very little money
Know that Cube produces good stuff and bad stuff. Bought a Stereo 150 HPA 27,5+ frame end of 2017 at bike-discount.de and this bike is just great. Frame was around 350 GBP and total bike (all new stuff) around 1500 GBP…(I use 2.6 inch tyres and 35 mm i.d. rims on the bike. A blast!). Bit of a downhill sled.
Right now, here and there: SC Bronson frames for sale? But guess they are still a bit over 1 k, means above your budget ?
As mentioned above: Calibre Bossnut is a decent trail bike (but lousy pre-assembly from Calibre…) One of the bikes I have is a Bossnut V2. Upgraded to 30 mm i.d. rims, DT370 hubs and 140 mm Fox 34 Fit4 fork.
Yes – 1 k is a great deal for the bike and used the bike with stock parts for over a year. Waited for some sales at CRC and winter sales for custom wheels. Yes – great trail bike. But with all the upgrades also around 1.5 k …