Yes, for example there is /c/balconygardening here on the SLRPNK Lemmy and all the moderators of that community with an SLRPNK account can also edit the community specific wiki over here: https://wiki.slrpnk.net/balconygardening:start

These permisions are automatic and you can create as many wiki pages as you like under the specific wiki namespace.

Edit: Let me see if there is a nice QR code externsion for Dokuwiki that I can add. Edit: Ah: if you click on the menu and select "Export as PDF" the resulting PDF also includes a QR code to the page already.

Edit2: after reading your post again: yes you can of course also just link to external already existing website in a new Lemmy community that you create here.