Use the sporty self-registering factory technique (of Bartlomiej Filipek)

[xparq]

https://www.cppstories.com/2023/ub-factory-constinit/

Also, a comment there from kstolze-ocient, with the details of a similar/alternative approach:

• https://github.com/fenbf/cppstories-discussions/issues/120#issuecomment-1608006513