I thought similar while setting up my wifi-only Gemini. I assume it has an IMEI because the chipset has eSIM support. You can get rid of the 'no sim' (or any) icon in the pull-down notification area by tapping the pencil icon and dragging what you don't want to the lower panel, but irritatingly it's still there in the top-of-the-screen notification strip.
I might try to install whatsapp, can't say I noticed what other phone-specific apps were available on the play store.