Does a GFCI also protect against arc faults?
You have it easy, since they added the GFCIs near the panel
So they did &quot;my trick&quot;, which is install a junction box right next to the panel and use GFCI receptacles rather than GFCI breakers.  There are two reasons to do that, #1 GFCI receps are way cheaper than breakers, and possibly #2 can't get GFCIs for obsolete panels. For instance Pushmatic is the best consumer panel ever made, but no GFCIs available for it.
So with the hard part done, an AFCI upgrade is a piece of cake: Swap the GFCI recep for a GFCI+AFCI recep.
That was easy!
But before you do that, look closely at the existing &quot;GFCIs&quot; as you call them.  The &quot;last guy&quot; was pretty smart, and may be way ahead of you.  They may already be AFCI or AFCI+GFCI deadfronts.
By the way, they don't have to be deadfronts unless they power kitchen, bathroom or laundry room.  Feel free to use plain receps there for all other circuits, just pinky-swear you won't plug - no I'm kidding. Feel free to plug in anything you want.
GFCI's provide partial arc-fault detection
Generally we're interested in 5 kinds of arc faults:

Arcing between hot and ground wires  &quot;parallel H-G fault&quot;
Arcing between neutral and ground wires &quot;parallel N-G fault&quot;
Arcing between hot and neutral wires &quot;parallel H-N fault&quot;
Arcing in the hot wire, in series with the load
Arcing in the neutral wire, in series with the load

The first two, parallel arc faults to ground, are easily detected by a GFCI because they are, after all, ground faults.  In fact most AFCIs detect those by having a weak GFCI detection right onboard - that's why AFCIs need neutral.
Of course it's hard to have a parallel conductor-to-ground fault if you don't have ground.  Assuming you don't have ground. A lot of older wiring used metal jacketed cable, which provides varying degrees of grounding (certainly good enough to trip a GFCI)... and some uses metal conduit, which is an approved grounding method today.