I bought my son a new bike frame. It has Boost rear spacing, and the current wheel is a 142×12 Hope Pro2 (not Evo).

I’m guessing I’m screwed and need to rebuild the wheel with a new hub?

There is a way. Kinda.

You can convert a Pro2 to Evo with an Evo axls and the right bearings, then an Evo freehub.

You can then use the Pro4/Pro2 Evo boost converter end caps.

Or velosolo spacers on the normal Pro2 end caps and a disc spacer.
https://velosolo.co.uk/shopmisc.html

You can get spacer kits to make any 142 hub into a boost. Not especially elegant but simple. You’ll need to dish the rim a little.

https://www.wiggle.co.uk/brand-x-rear-boost-conversion

Ah, cunning, thanks.

As for now I’ll be running 26″ wheels in the frame I might be able to get away without redishing the wheel.

You can get kits with a spacer each side so no dishing required, the chainline might be slightly sub optimal but I’ve not had any issues as it’s only a few mm

I run two bikes with boostinators on. The work absolutely fine. No issues whatsoever

Highjacking this thread.

I fitted a boost kit to my sons rear wheel but wondered if this puts the casette in a wierd place regarding chainline. He is running non boost cranks. Any issues with this set up, should he be running boost cranks or a spacer on chainring?

Thanks

With a non boost crank it’ll be fine if you’re running a spacer on each side of the wheel.
You’re basicaly running a non boost crank with a non boost chainline.
Just adjust the mech over accordingly.