- UTM / Create New Virtual Machine / Virtualize / Other
- Select 'Skip ISO boot' / Continue
- Hardware / (adjust as needed) Continue
- Storage / (adjust as needed) Continue
- Shared Directory / Continue
- Select 'Open VM Settings' / Save
- Right-click on Devices/Display and select Remove
- Devices / New / Serial
- Drive / New / Import and select install73.img
- Edit the VM again and move the second VirtIO Drive to the first position by right-clicking on it and selecting 'Move Up'
If you feel inclined, hop on to the UTM Discord and the folks there (me included) should be able to help out.
Anyone have tips on how to boot OpenBSD with UTM?