Remember my preference and go straight there next time (in this browser)
- which Riot web client URL to use; whether to go straight there;
- which matrix.to URL to redirect to; whether to go straight there;
- whether to go straight to the corresponding matrix: scheme URI;
Adding the option to "go straight there" -- redirect without intervention -- will enable this service to get out of the user's way (after the first visit per browser) and so be more convenient, more like using a real matrix: URI scheme.
- MAY have a delay before redirect to let the user see and possibly interrupt.
- MUST have a way to cancel the auto redirection, e.g. during delay or by visiting the base URL; should be discoverable.
Advanced: These preferences could be separately selectable per the server-name part of the entity address. That could be useful where a user has accounts on more than one homeserver, e.g. on example.org and on mozilla.org. These preferences could be separately selectable per entity kind (user, room, etc.), although that is probably less useful and over-complicated.
Storing the preferences in the user's browser's local storage is the first useful step. This will significantly lower the barrier for repeat users.
Better solutions than browser local storage may be possible. I am assuming that there is no intention to store data on the "matrix.to" domain, so only client-side solutions are in scope at the central "matrix.to" site. If the central matrix.to service can delegate to federated "matrix.to" services in any way (see #3), then server-side storage may be an option in those.