Unfortunately, the answer is no at the moment.
PowerShell Core 6.0 is built on top of .NET Core 2.0 runtime. But the thing is, PnP PowerShell depends on PnP CSOM Core components which are dependent on SharePoint CSOM libraries. Now, SharePoint CSOM libraries are dependent internally on some "other" libraries which are, as yet, not compatible with .NET Core.
Once, the CSOM libraries are ported or made compatible with .NET Core, we will be able to use it in PowerShell Core 6.0 and above.
Uservoice - Support .NET core with CSOM
There is this uservoice link where Microsoft has mentioned that they are looking into this thibg but has no ETA mentioned.
Also, I am assuming that you need to "do something cross-platform" , on a non-windows machine, if so, I would suggest that you take a look at
Office365-cli using which you manage any Office 365 tenant from any platform. Currently, the commands available are limited compared to PnP PowerShell but its growing quite fast. Office 365 cli internally calls the RESTful API endpoints which are platform agnostic.
References - Office365-cli
Managing Office 365 on any platform
Office 365 comparison with SPO and PnP PowerShell