I’ve used old BlackMagic Analog to SDI, & SDI to HDMI converters to get a digital signal. They work if the signal is a broadcast standard and constant. I know for dubbing digital video to VHS, I had to loop the analog signal (vga to composite (yellow rca), through a DVD player, and then into the VHS deck. The VGA forces a constant signal, but can reach odd results and mess with the tracking for VHS decks. The DVD player acted as a thru-put that corrected the issues in that signal and passed a desired NTSC standard into the VHS deck. Similarly, I know people use a camera to keep a projector from dropping the signal with Tachyons+. As someone mentioned in another comment, USB webcams have come a long way. Likewise, a lot of cheap USB capture devices like EasyCap act as web cams. I’ve used an EasyCap with OBS and NCH “Debut” software for RCA and S-Video capture via USB.
Hope it helps.