Why OpenBSD as a desktop? I like how simple and reliable it is. This guide is the shortest way to try OpenBSD on your hardware. This may take just few minutes. Read the official FAQ first.
Prepare a bootable USB drive. By the way, here is the step-by-step instruction for macOS.
Backup everything. As you follow this guide you may accidentally erase your drives, so before we continue, please back up all your data and verify your backups.
Enable full disk encryption, if you want to.
Boot from that USB drive. If you can't boot OpenBSD try to enable legacy-boot in your BIOS.
(I)nstall and answer the questions. Some hints:
If everything is okay:
...and unplug the flash drive.
Boot OpenBSD from your drive, login as root, and run:
Set URL to download packages and updates
echo 'https://cloudflare.cdn.openbsd.org/pub/OpenBSD'\ > /etc/installurl
Allow the user to run commands as root
echo 'permit nopass romanzolotarev'\ > /etc/doas.conf
Done. Reboot and login as a regular user.
Install a tilling window manager and Firefox.
doas pkg_add firefox
cwm your default window manager and start X11.
echo 'cwm' >> ~/.xinitrc startx
As you may expect, these steps are easy to automate as well. Check my post-install script.
Tested on OpenBSD 6.3.