[Pseudoscience-is-malarkey (OP)]

Do they simply orbit the condensed center of the galaxy, which acts as if it's one gigantic gravitational force? Do we not know the answer?

[evan_au]

It is thought that most spiral galaxies with a central bulge have a Super-Massive Black Hole (SMBH) at the center, with a mass about 0.1% of the central bulge.
See: https://en.wikipedia.org/wiki/Galactic_bulge#Central_compact_mass

Elliptical galaxies are thought to form from the merger of other galaxies, and have stars travelling in every axis, so any central bulge is impossible to discern. But it wouldn't surprise me if the SMBHs of the original galaxies are orbiting somewhere in the mix, stirring everything up.

The Magellenic clouds are dwarf galaxies that appear to be tidally disrupted by a close encounter with our galaxy. They are orbiting the center of our galaxy, as a satellite galaxy. The stars have been torn apart and now form a diffuse cloud, rather than orbiting a SMBH. Perhaps the Gaia space telescope may be able to find streams of stars that have been torn away from these dwarf galaxies?

For a unexpected case: https://astronomy.com/news/2018/08/teeny-tiny-galaxy-with-a-supermassive-black-hole

[Eternal Student]

Hi,

   Although not certain, it seems very likely that most (if not all) spiral galaxies contain a supermassive black hole and sometimes more than one.

[Taken from BBC Science Focus magazine:   https://www.sciencefocus.com/space/do-all-spiral-galaxies-have-black-holes-at-their-centre/]

  So you are talking about exceptional cases where a collection of stars exist and stay together in the general shape of a spiral galaxy but don't have a SMBH (Supermassive Black Hole) at their centre.  Until recently this was thought to be extremely unlikely and completely ignored.

   The general theory for the formation of galaxies implies that a BH would have formed within the galaxy and it would grow in mass to become a SMBH.   So the main explanation for finding a galaxy that does not seem to have a SMBH at it's centre is that the SMBH may have been "stolen" and merged into another SMBH when two galaxies collide.
[This PopSci artcile provides more information, if you're interested:   Forbes - "Ask Ethan: Why Doesn’t Every Galaxy Have A Supermassive Black Hole?"   https://www.forbes.com/sites/startswithabang/2021/04/23/ask-ethan-why-doesnt-every-galaxy-have-a-supermassive-black-hole/?sh=221078643374]

   In such cases (where two galaxies have collided), we need to recall that most of a galaxy is just open empty space:  Most of the stars and objects in those galaxies don't collide with each other or come into sufficiently close proximity with each other to seriously affect the momentum that they have.  So the galaxies appear to pass through each other.  It just might be that the two SMBH have come into close contact and the more massive one has swept up the smaller SMBH which might spiral around the other SMBH for a while and is likely to eventually merge.

   Over a large enough time, the two galaxies move apart and one is seen to be without a SMBH.  Where the distance between the galaxies is sufficient only the local gravity (the effect of mass within their own galaxy) should be important.  The galaxy without a SMBH should just behave like a swarm of particles. Usually there will still be some large-scale order and sense of talking about an average rotation of the galaxy around some central point.   The shell theorem suggests that the outer edges of that galaxy will still behave as if there is a massive single particle located at the centre.  However, the behaviour of a N-body system is notoriously complicated and chaotic.  I would anticipate that the centre of the galaxy shows behaviour that looks nothing like a regular orbit or rotation around a fixed point.   
   You asked what will the galaxy orbit around?  I would assume the outer edges seem to rotate around the centre of mass of the galaxy.  This will be just a point in space, it will not be the approximate location of an object like a SMBH any longer.  Meanwhile the centre of the galaxy becomes more chaotic and it may be very hard to identify an average rotation around any point.

NOTE:  That's my best guess, I haven't studied any specific models of such events and I don't claim to be an expert.
Late editing:   Looks like someone else has posted before I finished writing this.

[Janus]

The main take away is that the SMBH's at the center of galaxies represent only a tiny fraction of the total mass of those galaxies. For example, the estimated mass of our galaxy is 1.5 trillion solar masses, while the SMBH at the center is only 4 million solar masses,  If you removed Sagittarius A entirely, the vast majority of the stars in the galaxy wouldn't even notice.