On Mastodon, in settings > preferences > other there is an option to enable
<meta content="noindex, noarchive" name="robots">
header. This setting is per account and the noindex header is quite standardized. I would assume that similar setting exists for other platforms too (I did not check), because unwanted indexing could potentially invite unwanted users and spam, so proper indexing controls are a basic feature on any website, but especially for a whole social platform.
I'm not sure if a separate search lens for fediverse is needed. I'd be happy to try such if exists, but primarily I'd like to make sure that fediverse is at least somewhat discoverable, since that would make it more attractive to the mainstream. I tried to implement fediverse search lens on Brave search, but their index does not cover fediverse instances at all, so my Brave implementation is absolutely useless.
Kagi has this small web initiative and when I hear the word small web I immediately think about fediverse. I did consider submitting some fediverse instances to that project, but I am not sure if those fit into the project goal. I find it hilarious that youtube is acceptable platform for small web. I do not know if they accept peertube channels as submissions but I might try at some point.
Here is the Brave search goggle I created: https://codeberg.org/jimbo/bravegoggle/src/branch/main/fediverseonly.goggle. On each category there's a source and an explanation so even though it doesn't directly work for Kagi, it is probably good starting point. Or if this were to ever happen, I'd probably dump the whole list of fediverse domains there.
