The other percentiles do not appear to be moving much, but median has moved a fair bit. From the timeline, this looks like it corresponds to M55 going to Beta.

https://uma.googleplex.com/timeline_v2?sid=d2cc8a86d684c33c2cc0f0c96a6c9622

Analysis of Chrome-networking stats (Net.DNS_Resolution_And_TCP_Connection_Latency2) suggests a spike in value at median of Net.DNS_Resolution_And_TCP_Connection_Latency2 on Linux.
Channel	BETA
probability	9.0069e-06
value at median	48.97
recent median of value at median	41.99
MAD (past)	0.87
unit	ms
~samples	20 M
~users	197 k