Convert Sony Watcman/Magnavox Escort 2 from analog to digital tuning?
 

I was just wondering if anyone has converted one of these 80’s handheld TV’s to receive over the air digital signals? I have watched YouTube videos, but no one has tried to do this exact thing. Thanks!

Not enough room inside the case on almost all portables. About the best you could do is find a DTV converter box that's small and uses a wall wart of the same or lower voltage than the batteries, hook it in to the sets internal batteries, hot glue or tape it to the TV, connect the TVs whip antenna to the center lead of the antenna input on the converter box, then connect the TO TV coax on the box to the external antenna input of the TV (or where the whip used to connect on the TVs PCB, and have an ugly kludge...Also ATSC 1.0 sucks for any application where the antenna moves so you'll loose signal if you try to walk with it, use it in a moving vehicle, wind blows the antenna, etc. ATSC 3.0 is supposed to be better for mobile use but hasn't fully deployed yet, converter boxes for it don't support analog TVs and cost 3 figures.

I don't use my analog portables as away from home sets because of the downsides of mobile DTV reception and instead use my laptop and a tuner dongle for field use...I could use a portable DTV set if I wanted but the dongle was cheaper and uses less space when not in use.

How I use my portable analog sets within a block of home is by connecting the composite audio/video output of a DTV converter box or any video source I choose (in practice about 90% HDMI output of my media player PC and Roku down converted to analog) to a Blonder Tongue AM60 agile modulator feeding an antenna. The Blonder Tongue acts as a low power analog TV transmitter and any TV on my property or the block for that matter (when output is set to max) can tune it.

I have converted a cheap Casio TV-770 for general modern use (for easy demonstrations), but in a harder way: I build a composite video input using the original antenna P2 socket/plug. Since this set is plenty and abundant, I don't bother about some butchering.
Now I can plug anything that has same video standard as this device.
And the external visual are not changed.

Like I said, is a harder way, since most sets, even portable ones, have larger video signal amplitude than the composite video (some sets have whooping 4Vpp, and composite video and cousins have maximum 1Vpp), so it sometimes upset sync separators and color demodulators. And it can introduces new grounding issues.
For example, if the intention is to glue a mini digital converter on TV back, using same power supply/battery, the direct video option will may introduce some interference due ground currents. The antenna method will isolate the devices, since is possible to couple with very small capacitor (so is easier).
A careful ground arrangement, of course, can mitigate eventual issues in direct connection (or different batteries for each device).

So...

The pros of using the antenna method, is safer to use, is original use for >90% of TV sets (all these not having a video input).

The pros of the video input method, is cleaner images on bad calibrated sets, and sharper images on color TV when using S-Video for example.