I would ask in the e/OS forum. The old thread was tagged with FP5. Scanning through the forum I also found a mention to mail support for a question related to reselling. You could reach out through https://murena.com/contact-us/ directly.
I have no comparison but was in a similar boat when the FP5 launched. I was not sure how long my phone’s cracked display would last. I installed e/OS manually at the time (a beta release) and can’t remember any substantial issues. I can’t compare with a preinstalled version because I did not order that.
I think there’s a forum. Perhaps ask there if they know when they’ll be back in stock?
We run Taiga and it seems to work fine.
If you want to link to external sources in a structured way and you don’t mind tweaking the looks, SolidOS (ot another SOLID app) has a task list/tracker.
I keep my personal tasks in org-mode or org-roam.