Library seems abandoned

Thank you.

You are correct.

Most libraries, not all, even some commercial ones I purchased, are dead at one point in time.

People got priority, of course.

However, dead or alive, is no problem. What matters is functionality and feature. Non-critical bugs are common and fine, workarounds would do in the least.

No plan to replace it, it is currently feature -complete, IMHO, however Mason alternatives exist:

• GridStack 3.x is much more robust, responsive, and less buggier. It has Layout Builder integration. It appears to be bloated at first glance, but actually no JS libraries are loaded at frontend whenever it acts as Layout builder with CSS frameworks like Bootstrap or Foundation, or even just Native Grid. The bloat was its admin interface which is hardly an issue for frontend usages. Frontends can go without its JS libraries.
• Blazy grids as formatter and views style, including its 3.x Blazy layout for Layout Builder. It only lacks of paragraphs, but can be easily added if any demand. What Mason and GridStack have has already been in Blazy, named Native Grid, in its simplest pure CSS form, even before those two modules existed. Blazy 3.0.7+ allows multiple Native Grids and Flexbox for medium and large devices with minimal JS. Previously, only large devices, and the rest are plain columns, due to pure CSS. Browsers' supports for Native Grid are great, except for IE and other minorities:
  https://caniuse.com/?search=grid

Thank you for clarifying