I'm thinking to another alternative, that I give for reference as I can totally understand that moving from XT to Deore/Alivio is a downgrade. But if you can't have exactly what you want, you have to make compromises and this compromise will depend at the end of you priorities.
There is a 46/30 chainring in the Alivio range (FC-MT210-2). It's rated for 9-speed, so using it with a 11-speed chain can be a big stretch. I'm personally using that crankset with a 10 speed configuration (FD-M3000 front derailleur, RD-M5120 rear derailleur, 11-42 cassette).
A bit more far stretched: the Giant Roam Disc 0 (not available in all markets) uses a M8000 XT in combination with a 46/30 chainring in 11 speed. If your LBS can order Giant parts, it might interesting to see if they can order that chainring as spare part.
If you go for this option, you'll also need another front derailleur. The options are quite limited there also: Microshift FD-M622G-B (used by the Giant Roam 0).
Otherwise, I mention it for reference: 68mm bottom brackets start to be used on hybrid/touring bikes. It's worth checking because, in that case, it opens the possibility of using a 46/30 GRX crankset (FC-RX600-11) and remain with your XT for the rear derailleur. You will probably need a GRX front derailleur though (I think the pull ratios are the same for road and MTB front derailleurs, but am not sure. If it's confirmed, you can keep your shifter, otherwise you'll need to find a shifter for flat handler bars with road pull ratios).
But before using a 46/30, it's important to check the frame clearance. Even more with GRX cranksets that they have a chainline slightly closer to the frame.