[qubes-users] Qubes OS 4.2: no more access to local ports?

I have for years done my development work using dedicated AppVMs that run podman (https://podman.io/) containers based on images from bioconductor (https://bioconductor.org/help/docker/) for project isolation and reproducibility - images are pushed on a per project basis into the registry of the gitlab instance I use.

The containers run a server instance of posit’s RStudio IDE (https://posit.co/products/open-source/rstudio-server) and are started mapping a local (AppVM) port to the corresponding container port (8787, both). In the AppVM, a browser is then pointed at localhost:8787 to access the IDE and work in the container.

After upgrading to QubesOS 4.2 I appear no longer able to operate like that. Containers start just fine, but the browser cannot connect to the IDE.
Is this a result of the new firewall engine? How to fix it? How to debug?

Thank you for any pointers?