Personally after using headscale for a while, I ended up going with Netbird.
I prefer the UI of Netbird, plus it's been extremely stable and straightforward to setup and configure.
my main issue with headscale was headscale-ui though, not headscale itself. So if the former works for you, then you I'd say go with it.
Is there any way we can allow users who have access to invite other users to access the website, or is the only option to have people who want access to reach out to us and we add them ourselves?
AFAIK, You’ll have to implement SSO in your app and handle what “invite” means there. If you use cloudflare you’ll need to put the list of emails there.
Will providing access this way allow us to have any userID from the SSO that we can use to facilitate user settings like favourites?
Your app will get Cf-Access-Authenticated-User-Emails and Cf-Access-Jwt-Assertion headers for the user. Would that be enough to implement what you need?
I use Obsidian + Syncthing. Works across all my devices (including iOS).