Stateless Password Managers, which Spectre is one of, have common problems that generally have not been solved by the many iterations or versions that exist.
Here are some blog posts and articles that have various criticisms:
Nov 22, 2016 - 4 fatal flaws in deterministic password managers - Tony Arcieri
Nov 23, 2016 - In defense of deterministic password managers - Mahdi Mohammadinasab
Jan 17, 2018 - Problems with pwdhash - sjoerdlangkemper
Jun 19, 2020 - Stateless Password Manager Usability - Amir Szekely(kichik)

They all basically repeat the same 4 issues:

Inconsistent password restrictions lead to creating a state.
Fixed or unchangeable passwords don't work, and other sensitive data such as credit card info, ID Numbers, etc is unstorable.
Password Iterations(having to change your password for some reason) requires creating a state.
Remembering multiple usernames for multiple websites is difficult, leading to the creation of a state.
Any solution that leads to the creation of a state requires syncing.

I have some solutions for these problems.

1. Inconsistent password restrictions lead to creating a state.

Thankfully, the solution to this one can be solved without creating a state, or at least, an individual state. The best solution for this one I think is a de-centralized database (possibly blockchain) that keeps a record of various website's abnormal password restrictions and requirements. This is already public information, all one has to do is sign up for the website and they'll find out what the restrictions are, so keeping this saved to an individual state isn't necessary.

2, 3, & 4 all lead to the creation of a state.

The solution to the problem of having to create a state is a matter of implementation. Where do you store the state, and how do you transmit the state between devices?
My proposed solution is to have the process of transferring state be as convenient and easy as possible, while simultaneously being as secure and safe as possible.
Imposed Limitations:
No central server or cloud storage of state. This excludes using Google Drive or DropBox.
Minimal user input in process.

With those imposed limitations the only ways to pass the state from one device to another are using these different processes:
1) QR Codes generated in the App, presentable on the screen, and sharable/printable. With Covid everyone knows how to use these. The downside is that now the app needs access to the camera. Upside is that it is platform agnostic, so as long as you have your master password, you can take anyone's phone, download the app, enter your master password, and aim the camera at the QR code and you have your entire state loaded with no internet connection required. If you print it off and keep it in your wallet you can wipe your phone of state after every use if so be it.
2) For updates and and sync between devices, it depends on the device ecosystem. If using Android devices, the App should be able to update and sync with other instances of the app on other devices using the WiFi Direct protocol.
For Apple devices, the MultiPeer Connectivity Framework would be something to consider. This should allow Apple devices to push state updates to each other again without requiring and internet connection.
I don't have a solution for bridging the Apple Android divide for devices that don't have a camera that doesn't involve connecting to the internet or using some sort of file transfer app.

-Thoughts?