Filebeat dies on startup with 32-bit Ubuntu

Trying to start Filebeat crashes because it can't create the registry directory.

2019-07-29T00:32:18.905+0100	INFO	registrar/migrate.go:104	No registry home found. Create: /var/lib/filebeat/registry/filebeat
2019-07-29T00:32:18.905+0100	ERROR	beater/filebeat.go:302	Could not init registrar: failed to create registry dir '/var/lib/filebeat/registry/filebeat': mkdir /var: file exists
[...]
Exiting: failed to create registry dir '/var/lib/filebeat/registry/filebeat': mkdir /var: file exists

This seems like a bug, as it shouldn't be trying to recreate the /var directory. How do I fix this?

I've also been able to reproduce this on an Ubuntu 16.04 system, both this and the previous system were 32-bit.

I tried installing filebeat on a 64-bit Ubuntu 18.04 system and that worked okay. Potential bug with 32-bit filebeat?

I tried downgrading filebeat to 7.1.1 and this fixes the issue -- seems to be a bug in 7.2.0 on 32-bit systems. What's the best way to go about reporting this issue and getting it fixed?