How to rebuild the ports tree?

I'm stuck. I need to install the UniFi 6.2.26 port, I used the [FAQ to
setup the ports tree](https://www.openbsd.org/faq/ports/ports.html).
This seemed to work just fine. However, the last few messages in the
`make install` output showed errors. To debug the issue, I decided to
completely uninstall the UniFi port then pipe the `make install`
output to a log.txt.

To uninstall:

- TRIED: `make uninstall`
- ERROR: `make: don't know how to make uninstall`

- TRIED:
- `make clean`
- `pkg_delete -a`
- `make clean=dist`
- `make clean=packages`
- `make install`
- ERRORS: MANY (attached)

The question is, how to I just rebuild the ports tree and/or get it
back in a known good state?