How to make a 1x city bike easier to ride uphill?
I'm a big fan of low gears (I run a 22 inner ring on my MTB despite being a fairly strong climber), but I'd say a 22 or 24t ring is too small to use as an only ring - it'll spin out much to easily on slight downhills or with tailwinds.
You can get 1x cranks for MTB that come as standard with a 30T ring, and aftermarket 28T rings - I'd suggest these would be a better compromise.
As another alternative, if you are doing a conversion anyway, perhaps you might like to consider an aftermarket e-bike conversion?