I was for no reason I know of mulling over the possible problems with modern TVs vs Spectrum modulated video output. I have no idea if modern TVs continue to have analogue tuners but I suspect they may still retain them for use with video recorders and the like.
I recalled though, the BBC micro circuit diagram that I spent so many hours poring over with various degrees of comprehension (often not much) and the simplicity of the video circuitry that accepted the output from the video generator and sound magic chips and created the RGB, Composite Video and Modulated UHF outputs - in that order.
The Spectrum of course must be very similar!
A quick google
zx spectrum composite video mod
And of course someone has done it. One brave soul seems to have a no-soldering option.
The idea is to intercept the video signals before the UHF modulator and lead them out of the case.
I have not looked at any of the material since I do have a spectrum but there are options.
Then there is the sound?
TVs have composite video in and SCART and VGA are both pretty much RGB.
No-Soldering Sinclair ZX Spectrum 48k Composite
Google
zx spectrum scart video
ZX Spectrum - SPECTRA SCART Interface
The SPECTRA interface is a multi-purpose peripheral for the 16K/48K ZX Spectrum. Its primary function is to allow the Spectrum to be connected to a TV via a SCART socket to produce an RGB picture that is sharp, bright and free from dot-crawl.
My suggestion is not to bother, get a simulator/emulator for you PC if you must have that '80s exerience.