Safari and Chrome intermittently slow to load pages, taking about 30 seconds

(I'm on a MacBook Pro Apple M1 2021 16 in, 4 processors, Ventura 13.1)

About every 5 to 10 browser pages loads, my browser page load is very slow, taking about 30 seconds. The progress indicator on Safari stalls at about 10% and then takes a total of about 30 secs to load. Occasionally, the page doesn't load at all and I get a generic "Unable to open web page" message. I only use Chrome for Google docs, which I keep on on the same page (little navigation), and so it's difficult to say if this happens on Chrome. When this happens I sometimes open a Firefox window or a fresh Safari window and select a simple fast like like google.com, and I see the same slowness. All browsers then load the new page at about the same time.

This feels like a tcp connection race condition in some shared connection pool or such. E.g., I tend to keep many browser windows open simultaneously -- maybe Safari or Google Docs / Chrome is not releasing connections properly, exhausting the connection pool, and that 30 seconds is the timeout on unused connections being release back to the pool.

Related facts:

• This has been going for me for about the last 9 months. I update OSes immediately as they come so this corresponds roughly to the intro of Catalina. I've had the M1 for 13 months and I don't recall this problem in the first few months.
• I've tried suggestions I've seen on other Q&As: clearing my Safari history, restarting in Safe mode, and changing settings for data sharing. None of those worked.
• Every other activity on this computer is lighting fast, and I do fairly heavy work as a software developer. This is the odd duck.

Yes I entered a similar question / issue several months ago. Same problem after Ventura 13.0 and 13.1, so here I am again.