The question of strange matter and strange stars is an active area of research. Lot's of papers are published currently about this. There are two main direction of this research: 1) strangeness in astrophysics, e.g. https://arxiv.org/abs/2108.05606 and 2) strangeness production in very high-density hadron collisions, e.g. https://arxiv.org/abs/1510.07265 . Those papers are not very special, they are just examples.
Concerning 1), indeed, it is the assumption that multi-strange baryons will be much more tightly bound and will form very stable objects. Energetically, it may then be advantageous if the strangeness starts growing to further enhance this effect. This is similar to the fact that neutrons in nuclei are stable because they cannot decay since there is no "room" for them to decay into. However, the entire existence of "strange matter" is a hypothesis. It is not proven, nor is there any observational evidence that actually exists. In a star, it would be more like a neutron star than a black whole. If you consider a neutron star to be a super-massive nucleus out of nucleons (not 100% neutrons, either), a strange star will be the even higher-density version of this where a large part of the quark matter is converted into strange matter. There is nothing special about a strange star, it would behave and (from the distance) look just the same as a neutron star. Observationally, even with a huge telescopes an astronomer will not be able to distinguish the two things. However, there are ideas that you may observe the difference via specific energy-loss processes as they happen in pulsars: "pulsar glitches" are events related to the inner structure of the objects. A very good paper on this is https://www.nature.com/articles/359616a0 All of this is ongoing research. No conclusions yet. No evidence for any actual strange matter in the universe.
Concerning 2) there is research at accelerators to try to understand the possible formation of strange matter. Theoretically you can produce super-dense blobs of matter for super-short times in the collisions of very-high energy nuclei at LHC, or RHIC, etc. There even was the fear that this may be very dangerous, since "strangelets" may destroy the earth. However, there is concrete proof that this is not dangerous and will not happen: natural cosmic rays are bombarding the earth since billions of years at energies orders of magnitudes higher than even LHC. If strange matter could possibly be produced in high-energy collisions, it would for sure have happened in natural cosmic ray collisions. This is not the case. Again, there are no signs and no evidence for any actual possible production mechanism of such matter.