We recently refactored an SPA app with Hotwired using the StranglerFigApplication approach. This allowed us to add new page in Hotwired while incrementally replacing the old pages over time. We took it one page at a time. We made the navigation look mostly the same. Navigating the app users move between the SPA and the Hotwired pages and did not notice they were moving between the two stacks.
We remove the last bit of SPA code a few weeks ago.