I haven’t had the need (or time) to test these out yet, but from v1.8.1 on:
<img>, <video> and <audio> tags with relative src paths are now rendered in Live Preview and Reading mode.
1.8.1 is currently in catalyst (beta) testing.
https://obsidian.md/changelog/2025-01-07-desktop-v1.8.1/
Previous feature request topic: