Trying to figure out a solution for ebook management and syncing between iOS and eink

I have been thinking it is time to get out of being locked into the Kindle ecosystem for my ebook management. But I am not sure how or if I can manage ebooks that would meet my desired functionality. I am working on downloading my Kindle books, stripping DRM, and organizing them in calibre on my Mac for now.

These are my most important functions to achieve:

- Sync reading position between an e-ink device and an iOS app wirelessly
- Organize by series on reading devices
- Load books to reading devices wirelessly
- Preferably able to sync/load from outside the home

I’ve been trying to read and figure stuff out, but my brain is going in circles or I find too many old or irrelevant results for me to make sense of anything. I am not inexperienced with technology, but my brain isn’t as agile as it used to be. Between my husband and I, I am sure we could figure out how to set up a variety of things, I just can’t figure out what direction to go in. I would welcome any insight anyone might have to share or other possibilities I am missing.

This is what I’ve picked up so far that might serve the purpose, but I can’t grasp all the details:

When people talk about Calibre Server, does this mean the Calibre linux installation using the calibre content server?

Calibre content server and an OPDS server are two different things, right? It seems like the content server is more likely to sync metadata. Does OPDS sync anything or is it only for downloading?

I’m willing to buy another eink device. I currently use a Kindle Oasis, but I don’t think it’s practical for doing what I want outside of the Kindle ecosystem. It seems like an Android e-ink device might be the best path to achieve easy syncing with iOS devices, presuming there are applications that can cooperate.

I see mentions of using calibre server on a linux, and we could probably figure out a way to get that set up, but is there any way to sync with it other than Calibre Companion, which it sounds like is not in a good place of development right now?

Bookfusion seems like it might be another potential solution? It’s looks a bit early days for the apps at present, because they lack some reading functions I would want and they don’t expose the series info, but it sounds like they are working on it.