Hello folks!
TXT - because as plain text.
tox.0x10k.com/bootstrapd-conf-ipv46.txt same as tox.0x10k.com/bootstrapd-conf.txt - node list IPv4 and IPv6 if IPv4 not found.
tox.0x10k.com/bootstrapd-conf-ipv4.txt - node list IPv4 only
tox.0x10k.com/bootstrapd-conf-ipv6.txt - node list IPv6 only
tox.0x10k.com/bootstrapd-conf-ipv64.txt - node list IPv6 and IPv4 if IPv6 not found.

If you need only Germany servers, you add "-de", only US just add "-us". Germany and US - just add "-de-us" like tox.0x10k.com/bootstrapd-conf-ipv46-de-us.txt etc.
Like this you can generate conf with specific nodes.

Same time new feature for people who want to update their nodes:
tox.0x10k.com/bootstrapd-conf-ipv46-1.txt - will show all nodes except #1
tox.0x10k.com/bootstrapd-conf-ipv46-fr-3.txt - will show all nodes from FR except #3
tox.0x10k.com/bootstrapd-conf-ipv46-de-us-8.txt - will show all nodes from DE and US except node #8

BUT tox.0x10k.com/bootstrapd-conf.txt - always work as tox.0x10k.com/bootstrapd-conf-ipv46.txt and show IPv4 and IPv6 nodes (if no IPv4 found)

Here is our regexp: /bootstrapd-conf-ipv([\d]{1,3})([a-zA-Z\-]{0,64})([\d\-]{0,3})\.(txt)