Shimano GRX groupset with mechanical brakes for CX/Gravel I'm going to upgrade my cyclocross bike with new 1x11 dedicated components. Currently bike has old 105 5700 groupset and cantilever brakes. Those mechanical brakes are the main problem - I don't want to go on hydraulic discs because I've got quite new and good wheels for rim brakes and not compatible frameset.

I see 2 solutions, but non of them seems to be ideal;

1. Buy GRX 1x11 group and mix them with road ultegra shifters. Is it possible to use front 2x11 shifter for 1x11 drive? (I don't see any problem with using only brake lever, and have shifting unnecessary)
Do you think ultegra shifters are ok for off-road? Maybye something from other shimano group is better? All I know is that GRX has special design which should give more comfort

2. Buy SRAM Apex 1x11 for mechanical brakes - seems to be easy solution but I have already road bike with ultegra and I'm not very convinced that using different shifting in 2 bikes is a good idea, especially when I participate in races both on road and CX.

I'll be very grateful for any ideas/suggestions
The 2019 European Champion thinks Ultegra is quite fine for off-road https://www.cxmagazine.com/bike-profile-yara-kastelijn-stevens-super-prestige-cyclocross even for the 2019/2020 season. And yes, she is using 1x, although with hydraulic brakes and Di2 (electronic shifting). Many professionals are using Dura-Ace with 1x.

There is a difference in the brake lever (perhaps only the Di2 lever, see the comments) in the GRX shifters to allow more efficient braking from the hoods, but it is not considered essential yet. Many people do without. All other top non-GRX shifters should be pretty similar as the Ultegra.

I do not know if the the unconnected left shifter would feel weird, as Michael suggests, but GRX would be the same. You have the option to connect the GRX shifter to your dropper post. But if you don't have one...

As for the Apex, the front part of the groupset is independent, so you can have it and as long as you are only using it for braking the only wierd thing that remains is having two shifters with a different shape o one bike. It might feel or look strange. If you change everything to SRAM, you would have to be switching shifting between bikes, but many people manage with that.