Looking at (free) alternatives to TeamViewer. So far have found Distant
Desktop (10-11 MB, just runs), AnyDesk Free (~3.7 MB, runs), NoMachine
(34 MB!, installs), and others.

Do they _all_ require access to a remote server, *including for initial
setup of the connection*, or do any of them work entirely standalone?
(I'm not talking of machines on the same LAN, but helping a friend
hundreds of miles away [with no VPN or similar].)

Presumably if they need a remote server, even if only to start the
connection, the free versions could stop working at any time. (And the
commercial ones, of course, but they're mostly only limited-time anyway
unless you keep paying, i. e. they're monthly [in some cases yearly
really] not outright.)
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

Experience is that marvelous thing that enables you to recognize a mistake when
you make it again. -Franklin P. Jones