For an out-of-the-box approach that can be rolled out quickly, I'd look into in-app guidance prompts (
Setup --> In-App Guidance)
Add in-app guidance to your org using clicks, not code. To engage
directly with your users, write your own content and include action
buttons to your chosen URL in the prompts. You can specify the target
audience and where the prompts appear and for how long.
At the very least, you could alert the user you had a release and provide an action button to your long release notes stored on whatever platform you'd like. Other configurations you can take advantage of:
- Only show the prompt to specific profiles (Admins, etc)
- Provide a button that opens a URL
- Specify the scheduled (start date, end date, times to show)
Likewise, if you have a big or new feature - you could make a prompt that specifically brings it to users' attentions on the given page.
There's even walkthroughs now (you can have 3 active ones for free) that can provide linked prompts.