More news from my build. The frame is a real DIY project.
First I had to ream the seattube to fit a seatpost in. Now, after pressing in the BB I had to take it out and sand down the BB area since it was both WAY wonky and too wide. Bottom of the BB was 0,7mm too wide, probably paint buildup. I had to make a tool to sand it flat. It's too late to hammer in the cranks now but the sanding seems to have narrowed the BB to spec. Furthermore, with the wonky BB I tried fitting in a 34t XT M8100 crankset, the 'faux bolts' that connect the chainring to the spider were 0,001 mm from the frame. I'll need to add a shim to move it outboard after all the sanding hopefully buys me enough space for it.