I have the same problem, similar config, but with OpenMediaVault as OS and Swag and Nextcloud AIO running in the same stack. As far as i see I have a lot of processes /usr/share/elasticsearch/jdk/bin/java that occupy most of the memory (25GB out of 32GB is atm occupied). Can this be a cause for it being so slow?
… I can try to start without the full text search functionality…