Came to say Velo Orange 63, but they're max 2.2". And they mean it, the extra 6mm of a 2.25" wouldn't fit.

Some things that might be useful though:

Problem Solvers Fender Flute
Portland Design Works Safety Tabs
Mud flap (either buy or make out of damp proof course)

Mudhugger? I don't have any problems fitting them to rigid forks.

Crud X-Large.

Udhuggerhere aswell

Rrar crudguard fitted into steerer via a cork and a woodscrew, with a set of U stays adapted from some velo orange spares?

dost thou meanest a standard hugger or the gravel un?

I'm using SKS Veloflex 65 on mine. 2 muddy rides in (and a few not muddy) and all good. Mine use mudguard eyelets but they also do a version with strap on mounts.
https://www.tredz.co.uk/.SKS-Velo-65-Mountain-29-Mudguard-Set-Incl-U-Stays_203822.htm

For mountain biking duties, as above: been running Mudhugger-type (cheapo version, can't remember which brand) for years. This is my old 26" mudguard on the current 29er which doesn't give quite enough coverage so I'll upsize at some point.
[img] [/img]

Helitape the fork legs if you're precious. I also find a strip of sticky draught excluder tape down both legs makes fitting easier. Something like this:

https://www.ebay.co.uk/itm/385154388169?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ajrcemizq82&sssrc=4429486&ssuid=fskVY7jvSgK&var=&widget_ver=artemis&media=COPY

Pic on a not well cleaned bike. Tyre is WTB Ranger 29x2.25

Rrar crudguard fitted into steerer via a cork and a woodscrew,

I used to have a 'The' steerer mounted guard - full moto look. It actually looked horrific, I'll try and find a pic later

Think the Crud XL will be a pretty good solution for you.  Have been using one for around 4 years on a carbon 29er fork without any issues.

old 26″ mudguard on the current 29er which doesn’t give quite enough coverage so I’ll upsize at some point.

I added a 4" flap made of 2 layers of black gaffer tape sandwiching the guard tip then cut to shape, it works well.

Are your forks std length or suspension corrected length (ie big gap between tyre and crown)?

If former then I’m using these on 29x2.6

https://www.sks-germany.com/en/products/bluemels-style-28-75-set-11841/

did shortern the front a little

I just use a Mucky Nutz Face Fender XL with some extra holes cut in it for the attachment ties so that it sits in the right position.

Is lack of stability for rough terrain the only reason people don't run full length mudguards on rigid forks? SKS 75 has tyre clearance for a 2.6".

The SKS 75 are very stable, still fine of any off-road suited to rigid riding. Only had the breakaway pop on the fron on larger drops, but since shortened the front been fine since.