

The platforms should provide inter-protocol bridging natively. Now we have to follow an unrelated (to either) account and hope that it not fails silently*. This should be a switch in the UI.
*at least one can follow bridged accounts from elsewhere without bridging oneself.
Did you mean Vivaldi? It features a sidebar already with their own Mastodon instance: Vivaldi Social featured as one of sidebar entries.
A Vivaldi account allows to use not only Vivaldi Social, but also to make a WordPress blog, with federation available too.