I think a big problem behind the reluctance of alternatives to the strictly chronical timeline on Mastodon is that people fear that too much power is taken out of their hands if they are introduced. But the fact is: it is already the case that we put a lot of trust in administrators to put the correct software in place. A strictly chronological timeline makes one thing less to worry about but basically, it only reduces the symptom of the problem. Instead, I think the real problem needs to be faced: take away the fear of users that their instances are not working as they are supposed to and give them the power to check themselves whether the instances they are on are actually doing what they subscribed to.
As the most important, I think of the following two:
- Defederation Tool: shows from which other instances your own instance defederated (I think that already exists).
- Timeline tool: is the timeline curated based on the algorithm the instance proposed.
If these are in place, you could check that you see the right posts by the right instances, which is already a nice thing to know to begin with and would at least me quite content for introducing custom timelines and thereby giving more power to the admins. And with the mentality of this being an important issue, there would always be someone trying to see if an instance is run as promised and most admins wouldn't bother trying to do bad things.
Additionally, the algorithms would need to be determinstic and data collected by the instance about the user downloadable.
PS: Of course admins are doing a great job here, also given that most of them are volunteers. I'm not saying they are bad people, I'm just saying there need to be tools to control what they are doing if more powerful tools will be introduced to them in the future like custom timelines.