this obsidian plugin lets you force certain modes when opening notes:

• Plugin page: Force note view mode
• https://github.com/bwydoogh/obsidian-force-view-mode-of-note

The description only mentions frontmatter, but the actual plugin menu provides a way to set particular folders and files as read-only (no frontmatter needed).

The obsidianUIMode: preview is setting will disable the editor.

primarily used to ensure i treat readwise exports as read-only