Today is "El Salvador day," so there's lots of news and lots of trading.

According to blockchain.info, block 699509 was timestamped 17:00 UTC and 699510 was timestamped 18:06 UTC -- a 66-minute interval. Isn't that quite unusual? If so, what might have been the cause?

I made that post because I thought it would be quite useful to someone like ... me! The topic subject is a remote GUI monitor for bitcoind (or -qt). Evidently this freeware open-source software got little attention and use, but it looked like exactly what I needed so I spent non-trivial time installing it. For users who don't care about the deficiency I noted it's a "nice monitor!" For those, like me, who do, it's disappointing. I have no connection with the author.

Thanks for the explanation, although in this instance I'm not persuaded by the rationales. If the thread is too old to take replies, I'm not sure why the OP isn't deleted.  There's no need to get into the weeds on this, but my suggestion stands.

May I suggest that, when the reasons are "other" that some guidance be provided so that I may "avoid posting things that need to be deleted"? The quoted email reports on a reply which was definitely on-topic, and I have no idea why it was deleted.

I understand that mods don't want to get into discussions of, i.e., arguments about, such decisions but might some variations of the boilerplate be assembled to provide a clue?

Nice monitor! However, it doesn't display peers having .onion (Tor) addresses.

It was a stupid misreading, out of context, of some phrase like "Bitcoin Core v0.12 and later automatically tries to connect to Tor" [following context omitted; in https://en.bitcoin.it/wiki/Setting_up_a_Tor_hidden_service], but I'm not sure that precisely was the source.

I'm sure tor is running. E.g., it shows in ps output and I can get Firefox to use tor by setting it to use tor's Socks proxy.

As mentioned in the OP I presumed Core uses tor by default even with no (relevant) changes to bitcoin.conf or to tor's configuration (torrc). I now know, with the prodding of your and other responses here, that presumption was incorrect. Thanks!

Installed Bitcoin Core 0.21.1 on a Ubuntu system, copied over the contents of the .bitcoin directory (including blockchain data) from another system on which I'd been running Core for years. Installed Tor, with which I've no prior experience. Started bitcoin-qt having only these parameters in ~/.bitcoin/bitcoin.conf:
dbcache=1024
datadir=[path to .bitcoin data directory on volume different from /home volume]
debug=tor

I presumed that Core defaults to using Tor for its output.

There were a sizeable number of connections, both in and out, and my blockchain was brought up to date. The only evidence I see of Tor in debug.log is numerous periodic instances of:
tor: Error connecting to Tor control socket
tor: Not connected to Tor control port 127.0.0.1:9051, trying to reconnect

--until I closed bitcoin-qt, which generated:
tor: Thread interrupt
Shutdown: In progress...
addcon thread exit
torcontrol thread exit

In neither the "New outbound peer connected" entries in debug.log nor in the Peers window did I see anything that specifically indicated Tor to me, but then I don't know what I'm looking for. I retained the debug.log and screenshots of the Peers window for review. I can issue CLI commands if helpful.

Excellent. Thank you!

Update: The .asc (PGP signature) file for that command was the one downloaded from the Electrum site -- the one that I cannot import into GPG. But if I try to use the one @NeuroticFish kindly provided, which I can import, I get:

I was able to import this one, thanks! (And I was able to independently verify that it's ThomasV's key).

Then, however...
In that procedure, at this step......all that happened was that it imported the key (again, with no apparent harm).  What did not happen was what the procedure said would happen:

Thanks, but the first thing I did was try to follow that procedure, which is linked to on the Electrum download page. At this step...
...I get the result "No keys found."

MacOS 11.5.1
I have PGPTools installed, but I thought showing CLI results would be useful here. In case it's not obvious, I'm not sophisticated w/r PGP.

TL;DR: The recovery seed is used to (re)generate a master seed, from all the private seeds for one or more coin types are derived in a deterministic fashion. Ledger Nano S is a Hierarchical Deterministic (HD) wallet.

So what? With a hardware wallet your private keys are never exposed to an internet connection. This is not true of a smartphone wallet.

To send and receive requires internet. Hardware wallets do not connect to the internet, but they can connect to a computer via USB and the computer can connect to the internet. The user's private keys never leave the hardware wallet; the hardware wallet can generate receiving addresses and sign send transactions. With a smartphone, the device storing private keys is directly connected to the internet, even if only temporarily.

Thanks; all is now well. One last (I hope!) question: should I use -resetguisettings on subsequent runs of 0.15.0?

I can't recall what I did the first time I ran Core years ago, but the current dialog box has the "Use the default..." radio button pre-selected, the "Use a custom data directory..." button not selected, and "/Users/[me]/Library/Application Support/Bitcoin" in the field in which a custom directory can be specified. (Entry in that field is disabled unless the custom directory button is clicked.) That is in fact where the data is, and indeed the dialog box says under that field, "Directory already exists. Add /name if you intend to create a new directory here." Then outdented underneath that, "When you click OK, Bitcoin Core will begin to download and process the full Bitcoin block chain..." Is the latter statement inaccurate in my case?

Mac OS 10.10.5 (Yosemite)

After getting the crash discussed in this thread, I tried the suggested remedy:...which brings up a "Welcome to Bitcoin Core" dialog box that says since this is the first time the program's been launched the entire blockchain will be downloaded. I guess I can do that, but do I have to?

Did I misapply the remedy by trying it only after running 0.15.0 without it and getting the crash, instead of on the first run?

SOLVED 

Problem summary: Upgraded Ubuntu to 12.04; found that AMD Catalyst 11.12 driver (a.k.a. fglrx 8.92) is incompatible with Xorg X server 1.13.0, which is in 12.04.2, which is the current release of 12.04 LTS (Precise Pangolin). There was also an issue of 12.04.2 having kernel 3.5, which is  incompatible with Catalyst 11.12's installer; it wants kernel 3.2.

Solution: install 12.04.1, which has xserver 1.11.3 and kernel 3.2.  Even after running Software Updater, which updates to 12.04.2, xserver stays at 1.11.3 and the kernel stays at 3.2. 12.04.1 is available here.

Yes, I had done that prior to the results I showed. I was following the procedure from the Unofficial Wiki for the AMD Linux Driver. I used the commands to create fglrx .deb packages from the AMD Catalyst 11.12 download and install the packages, plus aticonfig etc.

That returns a long list of fonts.

EDIT: However...