I can play loads of instruments - if you set the bar as "can you play a recognisable tune on...?" I hope I play bass to a decent standard, guitar to a 'good enough to have fun playing along standard' but other instruments are pretty much just to have fun on my own or learn a part for a home recording. I did play mandolin in front of an audience in 2019 🙂
Fretted string instruments are all much of a muchness in terms of chords and melodies. Just be able to 'swap' chords/scales between fourth and fifth interval tunings. Get guitar and mandolin and you can play something on almost any fretted instrument. For example, you can tune an 8-string bozouki like the any four strings on a guitar and have great fun with something that sounds and looks very different without really learning any new skills.Strumsticks are good, diatonic ones are impossible to play out of tune 🙂
Ukes, have re-entrant tunings designed by people who hate musicians, learn a few chords and chug... Banjos are unusual you can learn a few plucking patterns and otherwise ignore the fifth string, but mine needs major repair.
Keyboards are easy to plonk out a basic melody or chords but need skills beyond me to do both at the same time. I used to be a whiz on the Stylophone...
Blowing things, the fingering of basic recorder/pennywhistle/mini sax is fairly easy to get. Some are easier to make sound nice than others. I count do squat with a flute despite borrowing one for a fortnight. A proper sax or clarinet is hell - be pleased if you can make it honk one good note.
Things like harmonicas and drums are deceiving. Easy to get a very basic result but they have their own skill sets that make it hard to go past the very basics.
Fretless stringed instruments are different. Violin is so hard to get a nice, consistent tone.
Fretless bass I can play fine, but feel it should be classed as a different instrument to the fretted bass just as the double bass is unique. It benefits from a different left-hand technique to fretted bass and rewards you improving your ear.
Then there's spoons...