Yes Hubble found the first intergalactic stars in 1997. As to whether they have planets, I don’t know of any actual detection of planets around intergalactic stars. But most are thought to originate from galaxy collisions so just ordinary stars ejected from ordinary galaxies. So probably many have planets.
This is an artist’s impression of what the night sky would look like from a planet orbiting such a star from their original release - you’d see the misty patches of distant galaxies, but nothing else.
Hubble Space Telescope - Images
But they wouldn’t be anything like as bright as this. Bear in mind that the Andromeda galaxy, if we could see it as brightly as it appears in photographs ,would look as large as this:
Yes, That Picture of the Moon and the Andromeda Galaxy Is About Right
It would be a spectacular object. But sadly we just can’t see it at all except as a faint smudge on very dark nights just visible to those with good eyesight and all you can see is the very center of the galaxy, easiest seen with binoculars.
So - your night sky would consist of just the faintest smudges of distant galaxies which you’d see only with excellent eyesight on a dark night. Though of course that’s just for us, if we can imagine beings there with much better night vision than us, their night sky might be rather spectacular, filled with galaxies.
These stars may not be rare. Every time two galaxies collide they send stars into intergalactic space.
According to one recent observation of a distant dim glow, then it’s possible that half of all the stars in our universe are in between the galaxies, intergalactic rogue stars. Half of stars lurk outside galaxies
Stars also leave galaxies all the time even without mergers. Here is a superimposed series of images of a moving star believed to have been ejected from the Large Magellanic Cloud,
Credit: ESO, photographed by the ESO Very Large Telescope,
Then there’s a small very interesting population of these stars. Sometimes when a star goes very close to its galaxies central black hole it can be accelerated through a slingshot effect to a large fraction of the speed of light. Anywhere between one tenth and a third of the speed of light. Although astronomers have spotted some very fast stars, the so called “hypervelocity stars” they haven’t found any quite so fast yet. But there could be as many as a thousand of these stars in every cubic megaparsec. That’s quite a large region - the volume of a huge cube, 3.262 million light years on a side, but of those, hundreds will be giant stars so could be spotted in future all sky surveys. And the James Web Space Telescope would be able to do a spectroscopic analysis.
These stars would have traveled billions of light years across a large part of the universe since they formed. And they would be ejected along with any tightly bound planets. So they could be a way for life to spread right across the large areas of the universe.
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