ExtraLoginFields-Example not working with SpringBoot3

The ExtraLoginFields example provided for SpringBoot2 under https://github.com/eugenp/tutorials/tree/master/spring-security-modules/spring-security-web-login does not seem to have a SpringBoot3 equivalent.

I played around with the example at https://github.com/ottlinger/sb3-filter-problem

• SpringBoot2 is working perfectly well, but
• SpringBoot3 does not work.

A request on StackOverflow and trying to file a bug (https://github.com/spring-projects/spring-boot/issues/36723 https://github.com/spring-projects/spring-security/issues/13620) with SpringBoot directly did not yield any reasonable/helpful answer.

Thus I wanted to ask if you have a working example with extra login fields with SpringBoot3. I'd happily contribute in case you find above example app useful (including a cypress-e2e test).

Thanks for any hints/updates concerning SB3.