How to create/edit loader.conf.local

[Buckethead]

Relative newbie hear.  I recently updated to version 2.4.0 via the dashboard link, and now my box won't boot past

Timecounter "HPET" frequency 19200000 Hz quality 950

I have an Asrock J4205 board, and this seems to be a common problem with Apollo Lake processors that has been discussed in multiple threads here and on other boards.  I want to try a promising fix (same board, same error, fixed) discussed in one of those threads, but it requires creating and/or editing the /boot/loader.conf.file.  The problem is I have no idea how to do this.  This question has been asked several times on this forum, but none received a clear answer that is usable for a non-booting system.  For example, the line below is one response that I found.

..you can edit that file from Diagnostics > Edit File. It may not exist yet, so put in that path, click load, type in what you need, then save. Then reboot to activate the settings.

Since my system won't start I cannot access the Diagnostics page, I have only the options provided by the loader.  The loader provides a limited console, but typing "?" does not indicate edit or save commands or even anything that might be them.  I don't see anything resembling a text editor like I would use in linux, such as nano.

All help is appreciated.

[Derelict]

I would boot from a 2.3.5 USB drive. Don't reinstall.

You should be able to mount the disk using the emergency shell, edit the file, then boot from the disk.

Might be easier to just install 2.3.5, edit the file, upgrade to 2.4.2, and restore a config backup if you are not familiar with how to do all of that.