One round of testing has been done on the latest 5.3 candidate build on all supported platforms, Can you please publish pgadmin4 5.3 on www.pgadmin.org.
Due to issue found in the "itsdangerous" package latest version, we will have to create a candidate build again. Latest pgAdmin4 v5.3 candidate builds and source can be found at https://developer.pgadmin.org/builds/2021-05-18-1/