RCA splitter

You won’t go wrong with that Audioquest splitter. I have used that for a subwoofer line level hookup!

Splitters usually work fine for most analog connections.

INMHO the integrity of the connection is more important than the "quality.". That said AQ makes various topologies. They along with Morrow's are better than cheap Chinese plastic adapters..

I know this example is not the same, but I think it has some applicability here.  I was using a pair of Cardas RCA to XLR adaptors on a pair of unbalanced interconnects where the source had xlr outputs and the amp only had rca inputs.  Eventually, I had a pair of Xhadow xlr plugs installed on the interconnects at the source end.  The difference in sound was obvious.  The adaptors were masking detail, blurring image outlines.....probably other compromises as well.  It's been a few years so I don't recall the exact differences.

If money isn't much an issue, perhaps the better sonic solution would be to use a pair of Y-interconnects.   

My use is temporary, for comparisons primarily.

For Stereo you need two splitters.

Pair of Jacks on a Device may be too close together for splitter gizmo, while splitter cables preserves tight spacing on the unit (i.e. my Vintage McIntosh Preamp)

Length of splitter cable can move 'joint' up for easy access

This stereo kit is available to buy by the foot

https://www.amazon.com/ROCKRIX-Female-Speaker-Adapter-Splitter/dp/B08PKS42P6/ref=asc_df_B08PKS42P6/?tag=hyprod-20&linkCode=df0&hvadid=475825775681&hvpos=&hvnetw=g&hvrand=18138763782454415975&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003526&hvtargid=pla-1163174276384&th=1

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i.e. I temporarily hook up friend's equipment (or my other stuff) to my system by adding the splitter 'down/back there', then a pair of jacks at accessible height.

Permanent/semi-permanent split, then access less important.

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You might need 'two in' and/or 'two out' depending on what you are doing

Splitters and Y-connectors are fine. I'd defy anyone to tell when one is in use.