Latest #fedicat build supports the save home timeline position setting for platforms that don't implement the mastodon marker api, should work on pleroma, sharkey, etc. now. It just saves the timeline per account locally, will probably generalize it to handle other feeds like lists.
fedicat
the #fedicat Save Home Position option is now Save Feed Position, it applies to lists aka custom feeds also (but doesn't use the mastodon marker api, so it's just saved on device)