You should keep it around, per the Asahi docs themselves, and marcan provides some additional context in a reddit comment which I've also quote here:

Can, yes. Should, no. It is not supported right now. You won't be able to install Asahi if you first remove macOS, and removing it after requires messing with partitions using a USB boot image or similar, and will leave you without the ability to recover from certain problems without outright reinstalling macOS first, plus no firmware updates (which might become required in the future to enable certain features - do you really want to find out you can't play newer games because you need a GPU firmware update and you have to reinstall macOS for that?).

We'll have more options for this in the future, but right now we do not support it and if you go this way, you're on your own.

That all leaves multiple copies of recoveryOS of course, which is a stripped-down version of macOS itself. It is not possible to remove recoveryOS and keep your machine functional at all. It is basically part of your BIOS.

You could try using diskutil apfs resizeContainer <container ID> minimum (I don't 100% recall if the last argument is actually minimum but using the regular --help should give you the correct one) in macOS to shrink the macOS container to smaller than the Asahi installer typically allows, or use expert mode in the Asahi install script to override the macOS size check, possibly with fewer negative consequences than deleting it outright.

Sorry if you already know all this but I thought I'd add it here just in case!