Libre Office (writer, calc, etc) does a lot online at startup

[LordParityLastCountofRegister]

I found one similar, closed question with an answer I found unsatisfactory as nonspecific and lacking detail.

Whenever I start a Libre Office program, it spends several seconds doing undocumented WAN activities. It is not, as suggested in the answer to the closed question, looking for updates. Current settings do not include an update option at all.

When I am using VPN to an endpoint in Outer Elsewhere, Libre Office takes more than a minute to start up, likely a connection timeout.

I gave settings a bogus proxy server (127.0.0.1:999), and startup is now almost instantaneous. That says there is a lot going on over the WAN (600 MB/sec connection here) at startup. I seek a specific, detailed answer about what Libre Office is really doing. I am concerned about privacy.

[igorlius]

About which version of LO are you talking? (see. Help > About Libreoffice)
Also since you seem sure it is a network rrelated issue, can you check to which urls the connections are being established to?

[LordParityLastCountofRegister]

From Writer, Help, About: Version: 6.1.5.2 (x64)
Build ID: 90f8dcf33c87b3705e78202e3df5142b201bd805
I have no way to determine which URLs or IP addresses are being used, but I’m open to suggestions.

[igorlius]

If you are under Windows, you could try this

View TCP/UDP network activity of every application on Windows

and under linux you could use tcpdump or wireshark

[robleyd]

Wireshark is probably the best known network protocol analyzer

[LordParityLastCountofRegister]

Set up live_tc, put proxy settings back to default, issue is now irreproducible, despite having been stable for months since installation. Yet another scratch on my old, bald head. OK to close. If/when I find a way to reproduce the issue, I will start over and have network monitoring data in hand. Thanks for the fast responses.