Its a disc brake bike, so it is possible to put smaller wheels.

But moving to 20" ETRTO 406 instead of 24" ETRTO 507 would lower the bike of about 50mm when using the same width of tires (using wider tires 50 or 55mm in ETRTO 406 is probably not possible), bottom bracket and pedals 50mm lower is a lot lower.

There is also the possibility to move to 20" ETRTO 451 but as far as I know there are only narrow tires like 28mm in ETRTO 451 so it will lower the bike of about 35mm. There are few tires available in ETRTO 451 which is a major drawback.