There also is 5f00::/16, an crazy large block set aside for SRv6

"In SRv6, SR source nodes initiate packets with a segment identifier in
the Destination Address of the IPv6 header, and SR segment endpoint
nodes process a local segment present in the Destination Address of an
IPv6 header."

https://www.iana.org/assignments/iana-ipv6-special-registry/
https://datatracker.ietf.org/doc/html/draft-ietf-6man-sids

Index: bgpd.conf
===================================================================
RCS file: /cvs/src/etc/examples/bgpd.conf,v
diff -u -p -r1.23 bgpd.conf
--- bgpd.conf	24 Jul 2024 18:56:57 -0000	1.23
+++ bgpd.conf	24 Jul 2024 19:10:54 -0000
@@ -40,6 +40,7 @@ prefix-set bogons {
 	2002::/16 or-longer		# 6to4 anycast relay [RFC7526]
 	3ffe::/16 or-longer		# old 6bone
 	3fff::/20 or-longer		# docu range [draft-ietf-v6ops-rfc3849-update]
+	5f00::/16 or-longer		# segment routing SRv6 SIDs [RFC9602]
 	fc00::/7 or-longer		# unique local unicast
 	fe80::/10 or-longer		# link local unicast
 	fec0::/10 or-longer		# old site local unicast