When importing official Zabbix templates low level discovery rules are wrongly interpreted:
<discovery_rule>
<name>Mounted filesystem discovery</name>
[..]
<key>vfs.fs.discovery</key>
[..]
<filter>

{#FSTYPE}:@File systems for discovery</filter>
[...]
</discovery_rule>

Is interpreted as (see attachment):
Filter:
Macro: "{#FSTYPE}

"
Regexp: "@File systems for discovery"

With such Regexp discovery rule is not working.

The same is with net.if.discovery rule in official templates.

Regexp should looks like: "ext4|ext3|ext2" or be empty.