I’m assuming other apps and the Finder work normally? Is there anything special you can think of about the setup of the macMini? e.g. restricted user account, network attached storage, etc.
When you have time, can you try creating a new admin user account in macOS and test opening Obsidian in there? If you can open it, save the vault to /Users/TESTUSER/{VAULTNAME} and create a few test notes and folders within Obsidian.
I’m wondering if the issue is isolated to your main user account or system wide.