why acct? activitypub is the protocol name. acct seems short for account, that could refer to any number of different protocols and services. the server name alone may be insufficient to identify the protocol.
I guess the right way to do this might be to publish your webfinger URL, and have clients that can read that and open your app of choice for each bit of info listed...
People who preferred to use the web UI could install a small helper app if wanted that would just construct the right web URL and open it with the default browser.
A big challenge for new Mastodon users is the inability to provide a one-click 'follow me on Mastodon' link. (A link to your profile takes others to *your* server, but they need to follow you on *theirs*, so have to take steps to copy the details over.) There are various hacks, such as Javascript bookmarklets, to deal with this, but I wondered whether any of the common client apps recognise a URL scheme, so you could link to 'mastodon://@quentinsf' and it would work for most people?