a) Set USERMAP_UID=0 and USERMAP_GID=0. Paperless will run as root inside of the container, which maps to your user's UID on the host. Some parts of #PaperlessNGX (e.g. Celery) might warn about running as root, but they don't refuse doing it.
b) Set USERMAP_UID=1000 and USERMAP_GID=1000 (or whatever they are on your host), add "user: 0" to each of the services in docker-compose.yml, start with PODMAN_USERNS=keep-id podman-compose up.